Sunday, August 17, 2008

PHP Database ODBC

Create an ODBC Connection

With an ODBC connection, you can connect to any database, on any computer in your network, as long as an ODBC connection is available.

Here is how to create an ODBC connection to a MS Access Database:

  1. Open the Administrative Tools icon in your Control Panel.
  2. Double-click on the Data Sources (ODBC) icon inside.
  3. Choose the System DSN tab.
  4. Click on Add in the System DSN tab.
  5. Select the Microsoft Access Driver. Click Finish.
  6. In the next screen, click Select to locate the database.
  7. Give the database a Data Source Name (DSN).
  8. Click OK.

Note that this configuration has to be done on the computer where your web site is located. If you are running Internet Information Server (IIS) on your own computer, the instructions above will work, but if your web site is located on a remote server, you have to have physical access to that server, or ask your web host to to set up a DSN for you to use.


Connecting to an ODBC

The odbc_connect() function is used to connect to an ODBC data source. The function takes four parameters: the data source name, username, password, and an optional cursor type.

The odbc_exec() function is used to execute an SQL statement.

Example

The following example creates a connection to a DSN called northwind, with no username and no password. It then creates an SQL and executes it:

$conn=odbc_connect('northwind','','');
$sql="SELECT * FROM customers";
$rs=odbc_exec($conn,$sql);





Retrieving Records



The odbc_fetch_row() function is used to return records from the result-set. This function returns true if it is able to return rows, otherwise false.



The function takes two parameters: the ODBC result identifier and an optional row number:



odbc_fetch_row($rs)





Retrieving Fields from a Record



The odbc_result() function is used to read fields from a record. This function takes two parameters: the ODBC result identifier and a field number or name.



The code line below returns the value of the first field from the record:



$compname=odbc_result($rs,1);


The code line below returns the value of a field called "CompanyName":



$compname=odbc_result($rs,"CompanyName");





Closing an ODBC Connection



The odbc_close() function is used to close an ODBC connection.



odbc_close($conn);





An ODBC Example



The following example shows how to first create a database connection, then a result-set, and then display the data in an HTML table.



<html>
<body>


<?php
$conn=odbc_connect('northwind','','');
if (!$conn)
{exit("Connection Failed: " . $conn);}
$sql="SELECT * FROM customers";
$rs=odbc_exec($conn,$sql);
if (!$rs)
{exit("Error in SQL");}
echo "<table><tr>";
echo "<th>Companyname</th>";
echo "<th>Contactname</th></tr>";
while (odbc_fetch_row($rs))
{
$compname=odbc_result($rs,"CompanyName");
$conname=odbc_result($rs,"ContactName");
echo "<tr><td>$compname</td>";
echo "<td>$conname</td></tr>";
}
odbc_close($conn);
echo "</table>";
?>


</body>
</html>

PHP MySQL Delete From

Delete Data In a Database

The DELETE FROM statement is used to delete records from a database table.

Syntax
DELETE FROM table_name
WHERE column_name = some_value


Note: SQL statements are not case sensitive. DELETE FROM is the same as delete from.



To get PHP to execute the statement above we must use the mysql_query() function. This function is used to send a query or command to a MySQL connection.



Example


Earlier in the tutorial we created a table named "Person". Here is how it looks:



























FirstName

LastName Age
Peter

Griffin 35
Glenn Quagmire 33


The following example deletes all the records in the "Person" table where LastName='Griffin':



<?php
$con = mysql_connect("localhost","peter","abc123");
if (!$con)
{
die('Could not connect: ' . mysql_error());
}


mysql_select_db("my_db", $con);

mysql_query("DELETE FROM Person WHERE LastName='Griffin'");


mysql_close($con);
?>


After the deletion, the table will look like this:



















FirstName LastName Age
Glenn

Quagmire 33

PHP MySQL Update

Update Data In a Database

The UPDATE statement is used to modify data in a database table.

Syntax
UPDATE table_name
SET column_name = new_value
WHERE column_name = some_value


Note: SQL statements are not case sensitive. UPDATE is the same as update.



To get PHP to execute the statement above we must use the mysql_query() function. This function is used to send a query or command to a MySQL connection.



Example


Earlier in the tutorial we created a table named "Person". Here is how it looks:



FirstName

LastName


Age



Peter

Griffin


35



Glenn

Quagmire


33



The following example updates some data in the "Person" table:



<?php
$con = mysql_connect("localhost","peter","abc123");
if (!$con)
{
die('Could not connect: ' . mysql_error());
}


mysql_select_db("my_db", $con);

mysql_query("UPDATE Person SET Age = '36'
WHERE FirstName = 'Peter' AND LastName = 'Griffin'");


mysql_close($con);
?>


After the update, the "Person" table will look like this:



























FirstName

LastName

Age
Peter

Griffin

36
Glenn

Quagmire


33


PHP MySQL Order By Keyword

The ORDER BY Keyword

The ORDER BY keyword is used to sort the data in a recordset.

Syntax
SELECT column_name(s)
FROM table_name
ORDER BY column_name


Note: SQL statements are not case sensitive. ORDER BY is the same as order by.



Example


The following example selects all the data stored in the "Person" table, and sorts the result by the "Age" column:



<?php
$con = mysql_connect("localhost","peter","abc123");
if (!$con)
{
die('Could not connect: ' . mysql_error());
}

mysql_select_db("my_db", $con);

$result = mysql_query("SELECT * FROM person ORDER BY age");

while($row = mysql_fetch_array($result))
{
echo $row['FirstName'];
echo " " . $row['LastName'];
echo " " . $row['Age'];
echo "<br />";
}


mysql_close($con);
?>


The output of the code above will be:



Glenn Quagmire 33
Peter Griffin 35





Sort Ascending or Descending



If you use the ORDER BY keyword, the sort-order of the recordset is ascending by default (1 before 9 and "a" before "p").



Use the DESC keyword to specify a descending sort-order (9 before 1 and "p" before "a"):



SELECT column_name(s)
FROM table_name
ORDER BY column_name DESC





Order by Two Columns



It is possible to order by more than one column. When ordering by more than one column, the second column is only used if the values in the first column are identical:



SELECT column_name(s)
FROM table_name
ORDER BY column_name1, column_name2

PHP MySQL The Where Clause

The WHERE clause

To select only data that matches a specific criteria, add a WHERE clause to the SELECT statement.

Syntax
SELECT column FROM table
WHERE column operator value


The following operators can be used with the WHERE clause:



Operator


Description



=

Equal



!=

Not equal



>

Greater than



<

Less than



>=

Greater than or equal



<=

Less than or equal



BETWEEN

Between an inclusive range



LIKE

Search for a pattern



Note: SQL statements are not case sensitive. WHERE is the same as where.



To get PHP to execute the statement above we must use the mysql_query() function. This function is used to send a query or command to a MySQL connection.



Example


The following example will select all rows from the "Person" table, where FirstName='Peter':



<?php
$con = mysql_connect("localhost","peter","abc123");
if (!$con)
{
die('Could not connect: ' . mysql_error());
}

mysql_select_db("my_db", $con);

$result = mysql_query("SELECT * FROM person
WHERE FirstName='Peter'");

while($row = mysql_fetch_array($result))
{
echo $row['FirstName'] . " " . $row['LastName'];
echo "<br />";
}

?>


The output of the code above will be:



Peter Griffin

PHP MySQL Select

Select Data From a Database Table

The SELECT statement is used to select data from a database.

Syntax
SELECT column_name(s)
FROM table_name


Note: SQL statements are not case sensitive. SELECT is the same as select.



To get PHP to execute the statement above we must use the mysql_query() function. This function is used to send a query or command to a MySQL connection.



Example


The following example selects all the data stored in the "Person" table (The * character selects all of the data in the table):



<?php
$con = mysql_connect("localhost","peter","abc123");
if (!$con)
{
die('Could not connect: ' . mysql_error());
}


mysql_select_db("my_db", $con);


$result = mysql_query("SELECT * FROM person");


while($row = mysql_fetch_array($result))
{
echo $row['FirstName'] . " " . $row['LastName'];
echo "<br />";
}


mysql_close($con);
?>


The example above stores the data returned by the mysql_query() function in the $result variable. Next, we use the mysql_fetch_array() function to return the first row from the recordset as an array. Each subsequent call to mysql_fetch_array() returns the next row in the recordset. The while loop loops through all the records in the recordset. To print the value of each row, we use the PHP $row variable ($row['FirstName'] and $row['LastName']).



The output of the code above will be:



Peter Griffin
Glenn Quagmire





Display the Result in an HTML Table



The following example selects the same data as the example above, but will display the data in an HTML table:



<?php
$con = mysql_connect("localhost","peter","abc123");
if (!$con)
{
die('Could not connect: ' . mysql_error());
}

mysql_select_db("my_db", $con);

$result = mysql_query("SELECT * FROM person");

echo "<table border='1'>
<
tr>
<th>Firstname</th>
<th>Lastname</th>
</tr>";


while($row = mysql_fetch_array($result))
{
echo "<tr>";
echo "<td>" . $row['FirstName'] . "</td>";
echo "<td>" . $row['LastName'] . "</td>";
echo "</tr>";
}
echo "</table>";


mysql_close($con);
?>


The output of the code above will be:





















Firstname Lastname
Glenn Quagmire
Peter Griffin

PHP MySQL Insert Into

Insert Data Into a Database Table

The INSERT INTO statement is used to add new records to a database table.

Syntax
INSERT INTO table_name
VALUES (value1, value2,....)


You can also specify the columns where you want to insert the data:



INSERT INTO table_name (column1, column2,...)
VALUES (value1, value2,....)


Note: SQL statements are not case sensitive. INSERT INTO is the same as insert into.



To get PHP to execute the statements above we must use the mysql_query() function. This function is used to send a query or command to a MySQL connection.



Example


In the previous chapter we created a table named "Person", with three columns; "Firstname", "Lastname" and "Age". We will use the same table in this example. The following example adds two new records to the "Person" table:



<?php
$con = mysql_connect("localhost","peter","abc123");
if (!$con)
{
die('Could not connect: ' . mysql_error());
}


mysql_select_db("my_db", $con);


mysql_query("INSERT INTO person (FirstName, LastName, Age) 
VALUES ('Peter', 'Griffin', '35')");


mysql_query("INSERT INTO person (FirstName, LastName, Age) 
VALUES ('Glenn', 'Quagmire', '33')");


mysql_close($con);
?>





Insert Data From a Form Into a Database



Now we will create an HTML form that can be used to add new records to the "Person" table.



Here is the HTML form:



<html>
<body>


<form action="insert.php" method="post">
Firstname: <input type="text" name="firstname" />
Lastname: <input type="text" name="lastname" />
Age: <input type="text" name="age" />
<input type="submit" />
</form>


</body>
</html>


When a user clicks the submit button in the HTML form in the example above, the form data is sent to "insert.php". The "insert.php" file connects to a database, and retrieves the values from the form with the PHP $_POST variables. Then, the mysql_query() function executes the INSERT INTO statement, and a new record will be added to the database table.



Below is the code in the "insert.php" page:



<?php
$con = mysql_connect("localhost","peter","abc123");
if (!$con)
{
die('Could not connect: ' . mysql_error());
}


mysql_select_db("my_db", $con);


$sql="INSERT INTO person (FirstName, LastName, Age)
VALUES
('$_POST[firstname]','$_POST[lastname]','$_POST[age]')";


if (!mysql_query($sql,$con))
{
die('Error: ' . mysql_error());
}
echo "1 record added";


mysql_close($con)
?>

PHP MySQL Create Database and Tables

Create a Database

The CREATE DATABASE statement is used to create a database in MySQL.

Syntax
CREATE DATABASE database_name


To get PHP to execute the statement above we must use the mysql_query() function. This function is used to send a query or command to a MySQL connection.



Example


In the following example we create a database called "my_db":



<?php
$con = mysql_connect("localhost","peter","abc123");
if (!$con)
{
die('Could not connect: ' . mysql_error());
}


if (mysql_query("CREATE DATABASE my_db",$con))
{
echo "Database created";
}
else
{
echo "Error creating database: " . mysql_error();
}


mysql_close($con);
?>





Create a Table



The CREATE TABLE statement is used to create a database table in MySQL.



Syntax


CREATE TABLE table_name
(
column_name1 data_type,
column_name2 data_type,
column_name3 data_type,
.......

)


We must add the CREATE TABLE statement to the mysql_query() function to execute the command.



Example


The following example shows how you can create a table named "person", with three columns. The column names will be "FirstName", "LastName" and "Age":



<?php
$con = mysql_connect("localhost","peter","abc123");
if (!$con)
{
die('Could not connect: ' . mysql_error());
}


// Create database
if (mysql_query("CREATE DATABASE my_db",$con))
{
echo "Database created";
}
else
{
echo "Error creating database: " . mysql_error();
}


// Create table in my_db database
mysql_select_db("my_db", $con);
$sql = "CREATE TABLE person  (
FirstName varchar(15),
LastName varchar(15),
Age int
)";
mysql_query($sql,$con);


mysql_close($con);
?>


Important: A database must be selected before a table can be created. The database is selected with the mysql_select_db() function.



Note: When you create a database field of type varchar, you must specify the maximum length of the field, e.g. varchar(15).






MySQL Data Types



Below are the different MySQL data types that can be used:



Numeric Data Types

Description



int(size)

smallint(size)


tinyint(size)


mediumint(size)


bigint(size)


Hold integers only. The maximum number of digits can be specified in the size parameter



decimal(size,d)

double(size,d)


float(size,d)


Hold numbers with fractions. The maximum number of digits can be specified in the size parameter. The maximum number of digits to the right of the decimal is specified in the d parameter



Textual Data Types

Description



char(size)

Holds a fixed length string (can contain letters, numbers, and special characters). The fixed size is specified in parenthesis



varchar(size)

Holds a variable length string (can contain letters, numbers, and special characters). The maximum size is specified in parenthesis



tinytext

Holds a variable string with a maximum length of 255 characters



text

blob


Holds a variable string with a maximum length of 65535 characters



mediumtext

mediumblob


Holds a variable string with a maximum length of 16777215 characters



longtext

longblob


Holds a variable string with a maximum length of 4294967295 characters



Date Data Types

Description



date(yyyy-mm-dd)

datetime(yyyy-mm-dd hh:mm:ss)


timestamp(yyyymmddhhmmss)


time(hh:mm:ss)


Holds date and/or time



Misc. Data Types

Description



enum(value1,value2,ect)

ENUM is short for ENUMERATED list. Can store one of up to 65535 values listed within the ( ) brackets. If a value is inserted that is not in the list, a blank value will be inserted



set

SET is similar to ENUM. However, SET can have up to 64 list items and can store more than one choice






Primary Keys and Auto Increment Fields



Each table should have a primary key field.



A primary key is used to uniquely identify the rows in a table. Each primary key value must be unique within the table. Furthermore, the primary key field cannot be null because the database engine requires a value to locate the record.



The primary key field is always indexed. There is no exception to this rule! You must index the primary key field so the database engine can quickly locate rows based on the key's value.



The following example sets the personID field as the primary key field. The primary key field is often an ID number, and is often used with the AUTO_INCREMENT setting. AUTO_INCREMENT automatically increases the value of the field by 1 each time a new record is added. To ensure that the primary key field cannot be null, we must add the NOT NULL setting to the field.



Example


$sql = "CREATE TABLE person  (
personID int NOT NULL AUTO_INCREMENT,
PRIMARY KEY(personID),
FirstName varchar(15),
LastName varchar(15),
Age int
)";


mysql_query($sql,$con);

PHP MySQL Connect to a Database

Connecting to a MySQL Database

Before you can access and work with data in a database, you must create a connection to the database.

In PHP, this is done with the mysql_connect() function.

Syntax
mysql_connect(servername,username,password);


Parameter

Description



servername

Optional. Specifies the server to connect to. Default value is "localhost:3306"



username

Optional. Specifies the username to log in with. Default value is the name of the user that owns the server process



password

Optional. Specifies the password to log in with. Default is ""



Note: There are more available parameters, but the ones listed above are the most important. Visit our full PHP MySQL Reference for more details.



Example


In the following example we store the connection in a variable ($con) for later use in the script. The "die" part will be executed if the connection fails:



<?php
$con = mysql_connect("localhost","peter","abc123");
if (!$con)
{
die('Could not connect: ' . mysql_error());
}


// some code


?>





Closing a Connection



The connection will be closed as soon as the script ends. To close the connection before, use the mysql_close() function.



<?php
$con = mysql_connect("localhost","peter","abc123");
if (!$con)
{
die('Could not connect: ' . mysql_error());
}


// some code


mysql_close($con);
?>

Saturday, August 16, 2008

PHP Filter

What is a PHP Filter?

A PHP filter is used to validate and filter data coming from insecure sources.

To test, validate and filter user input or custom data is an important part of any web application.

The PHP filter extension is designed to make data filtering easier and quicker.


Why use a Filter?

Almost all web applications depend on external input. Usually this comes from a user or another application (like a web service). By using filters you can be sure your application gets the correct input type.

You should always filter all external data!

Input filtering is one of the most important application security issues.

What is external data?

  • Input data from a form
  • Cookies
  • Web services data
  • Server variables
  • Database query results

Functions and Filters

To filter a variable, use one of the following filter functions:

  • filter_var() - Filters a single variable with a specified filter
  • filter_var_array() - Filter several variables with the same or different filters
  • filter_input - Get one input variable and filter it
  • filter_input_array - Get several input variables and filter them with the same or different filters

In the example below, we validate an integer using the filter_var() function:

<?php
$int = 123;


if(!filter_var($int, FILTER_VALIDATE_INT))
{
echo("Integer is not valid");
}
else
{
echo("Integer is valid");
}
?>


The code above uses the "FILTER_VALIDATE_INT"  filter to filter the variable. Since the integer is valid, the output of the code above will be: "Integer is valid".



If we try with a variable that is not an integer (like "123abc"), the output will be: "Integer is not valid".



For a complete list of functions and filters, visit our PHP Filter Reference.






Validating and Sanitizing



There are two kinds of filters:



Validating filters:




  • Are used to validate user input


  • Strict format rules (like URL or E-Mail validating)


  • Returns the expected type on success or FALSE on failure



Sanitizing filters:




  • Are used to allow or disallow specified characters in a string


  • No data format rules


  • Always return the string






Options and Flags



Options and flags are used to add additional filtering options to the specified filters.



Different filters have different options and flags.



In the example below, we validate an integer using the filter_var() and the "min_range" and "max_range" options:



<?php
$var=300;


$int_options = array(
"options"=>array
(
"min_range"=>0,
"max_range"=>256
)
);


if(!filter_var($var, FILTER_VALIDATE_INT, $int_options))
{
echo("Integer is not valid");
}
else
{
echo("Integer is valid");
}
?>


Like the code above, options must be put in an associative array with the name "options". If a flag is used it does not need to be in an array.



Since the integer is "300" it is not in the specified range, and the output of the code above will be: "Integer is not valid".



For a complete list of functions and filters, visit our PHP Filter Reference. Check each filter to see what options and flags are available.






Validate Input



Let's try validating input from a form.



The first thing we need to do is to confirm that the input data we are looking for exists.



Then we filter the input data using the filter_input() function.



In the example below, the input variable "email" is sent to the PHP page:



<?php
if(!filter_has_var(INPUT_GET, "email"))
{
echo("Input type does not exist");
}
else
{
if (!filter_input(INPUT_GET, "email", FILTER_VALIDATE_EMAIL))
{
echo "E-Mail is not valid";
}
else
{
echo "E-Mail is valid";
}
}
?>


Example Explained



The example above has an input (email) sent to it using the "GET" method:




  1. Check if an "email" input variable of the "GET" type exist


  2. If the input variable exists, check if it is a valid e-mail address






Sanitize Input



Let's try cleaning up an URL sent from a form.



First we confirm that the input data we are looking for exists.



Then we sanitize the input data using the filter_input() function.



In the example below, the input variable "url" is sent to the PHP page:



<?php
if(!filter_has_var(INPUT_POST, "url"))
{
echo("Input type does not exist");
}
else
{
$url = filter_input(INPUT_POST,
"url", FILTER_SANITIZE_URL);
}
?>


Example Explained



The example above has an input (url) sent to it using the "POST" method:




  1. Check if the "url" input of the "POST" type exists


  2. If the input variable exists, sanitize (take away invalid characters) and store it in the $url variable



If the input variable is a string like this "http://www.W3ååSchøøools.com/", the $url variable after the sanitizing will look like this:



http://www.W3Schools.com/





Filter Multiple Inputs



A form almost always consist of more than one input field. To avoid calling the filter_var or filter_input functions over and over, we can use the filter_var_array or the filter_input_array functions.



In this example we use the filter_input_array() function to filter three GET variables. The received GET variables is a name, an age and an e-mail address:



<?php
$filters = array
(
"name" => array
(
"filter"=>FILTER_SANITIZE_STRING
),
"age" => array
(
"filter"=>FILTER_VALIDATE_INT,
"options"=>array
(
"min_range"=>1,
"max_range"=>120
)
),
"email"=> FILTER_VALIDATE_EMAIL,
);


$result = filter_input_array(INPUT_GET, $filters);


if (!$result["age"])
{
echo("Age must be a number between 1 and 120.<br />");
}
elseif(!$result["email"])
{
echo("E-Mail is not valid.<br />");
}
else
{
echo("User input is valid");
}
?>


Example Explained



The example above has three inputs (name, age and email) sent to it using the "GET" method:




  1. Set an array containing the name of input variables and the filters used on the specified input variables


  2. Call the filter_input_array() function with the GET input variables and the array we just set


  3. Check the "age" and "email" variables in the $result variable for invalid inputs. (If any of the input variables are invalid, that input variable will be FALSE after the filter_input_array() function)



The second parameter of the filter_input_array() function can be an array or a single filter ID.



If the parameter is a single filter ID all values in the input array are filtered by the specified filter.



If the parameter is an array it must follow these rules:




  • Must be an associative array containing an input variable as an array key (like the "age" input variable)


  • The array value must be a filter ID or an array specifying the filter, flags and options






Using Filter Callback



It is possible to call a user defined function and use it as a filter using the FILTER_CALLBACK filter. This way, we have full control of the data filtering.



You can create your own user defined function or use an existing PHP function



The function you wish to use to filter is specified the same way as an option is specified. In an associative array with the name "options"



In the example below, we use a user created function to convert all  "_" to whitespaces:



<?php
function convertSpace($string)
{
return str_replace("_", " ", $string);
}

$string = "Peter_is_a_great_guy!";

echo filter_var($string, FILTER_CALLBACK,
array("options"=>"convertSpace"));
?>


The result from the code above should look like this:



Peter is a great guy!


Example Explained



The example above converts all "_" to whitespaces:




  1. Create a function to replace "_" to whitespaces


  2. Call the filter_var() function with the FILTER_CALLBACK filter and an array containing our function

PHP Exception Handling

What is an Exception

With PHP 5 came a new object oriented way of dealing with errors.

Exception handling is used to change the normal flow of the code execution if a specified error (exceptional) condition occurs. This condition is called an exception.
This is what normally happens when an exception is triggered:

  • The current code state is saved
  • The code execution will switch to a predefined (custom) exception handler function
  • Depending on the situation, the handler may then resume the execution from the saved code state, terminate the script execution or continue the script from a different location in the code

We will show different error handling methods:

  • Basic use of Exceptions
  • Creating a custom exception handler
  • Multiple exceptions
  • Re-throwing an exception
  • Setting a top level exception handler

Note: Exceptions should only be used with error conditions, and should not be used to jump to another place in the code at a specified point.


Basic Use of Exceptions

When an exception is thrown, the code following it will not be executed, and PHP will try to find the matching "catch" block.

If an exception is not caught, a fatal error will be issued with an "Uncaught Exception" message.

Lets try to throw an exception without catching it:

<?php
//create function with an exception
function checkNum($number)
{
if($number>1)
{
throw new Exception("Value must be 1 or below");
}
return true;
}

//trigger exception
checkNum(2);
?>


The code above will get an error like this:



Fatal error: Uncaught exception 'Exception' 
with message 'Value must be 1 or below' in C:\webfolder\test.php:6
Stack trace: #0 C:\webfolder\test.php(12):
checkNum(28) #1 {main} thrown in C:\webfolder\test.php on line 6


Try, throw and catch



To avoid the error from the example above, we need to create the proper code to handle an exception.



Proper exception code should include:




  1. Try - A function using an exception should be in a "try" block. If the exception does not trigger, the code will continue as normal. However if the exception triggers, an exception is "thrown"


  2. Throw - This is how you trigger an exception. Each "throw" must have at least one "catch"


  3. Catch - A "catch" block retrieves an exception and creates an object containing the exception information



Lets try to trigger an exception with valid code:



<?php
//create function with an exception
function checkNum($number)
{
if($number>1)
{
throw new Exception("Value must be 1 or below");
}
return true;
}

//trigger exception in a "try" block
try
{
checkNum(2);
//If the exception is thrown, this text will not be shown
echo 'If you see this, the number is 1 or below';
}

//catch exception
catch(Exception $e)
{
echo 'Message: ' .$e->getMessage();
}
?>


The code above will get an error like this:



Message: Value must be 1 or below


Example explained:



The code above throws an exception and catches it:




  1. The checkNum() function is created. It checks if a number is greater than 1. If it is, an exception is thrown


  2. The checkNum() function is called in a "try" block


  3. The exception within the checkNum() function is thrown


  4. The "catch" block retrives the exception and creates an object ($e) containing the exception information


  5. The error message from the exception is echoed by calling $e->getMessage() from the exception object



However, one way to get around the "every throw must have a catch" rule is to set a top level exception handler to handle errors that slip through.






Creating a Custom Exception Class



Creating a custom exception handler is quite simple. We simply create a special class with functions that can be called when an exception occurs in PHP. The class must be an extension of the exception class.



The custom exception class inherits the properties from PHP's exception class and you can add custom functions to it.



Lets create an exception class:



<?php
class customException extends Exception
{
public function errorMessage()
{
//error message
$errorMsg = 'Error on line '.$this->getLine().' in '.$this->getFile()
.': <b>'.$this->getMessage().'</b> is not a valid E-Mail address';
return $errorMsg;
}
}


$email = "someone@example...com";


try
{
//check if
if(filter_var($email, FILTER_VALIDATE_EMAIL) === FALSE)
{
//throw exception if email is not valid
throw new customException($email);
}
}


catch (customException $e)
{
//display custom message
echo $e->errorMessage();
}
?>


The new class is a copy of the old exception class with an addition of the errorMessage() function. Since it is a copy of the old class, and it inherits the properties and methods from the old class, we can use the exception class methods like getLine() and getFile() and getMessage().



Example explained:



The code above throws an exception and catches it with a custom exception class:




  1. The customException() class is created as an extension of the old exception class. This way it inherits all methods and properties from the old exception class


  2. The errorMessage() function is created. This function returns an error message if an e-mail address is invalid


  3. The $email variable is set to a string that is not a valid e-mail address


  4. The "try" block is executed and an exception is thrown since the e-mail address is invalid


  5. The "catch" block catches the exception and displays the error message






Multiple Exceptions



It is possible for a script to use multiple exceptions to check for multiple conditions.



It is possible to use several if..else blocks, a switch, or nest multiple exceptions. These exceptions can use different exception classes and return different error messages:



<?php
class customException extends Exception
{
public function errorMessage()
{
//error message
$errorMsg = 'Error on line '.$this->getLine().' in '.$this->getFile()
.': <b>'.$this->getMessage().'</b> is not a valid E-Mail address';
return $errorMsg;
}
}

$email = "someone@example.com";

try
{
//check if
if(filter_var($email, FILTER_VALIDATE_EMAIL) === FALSE)
{
//throw exception if email is not valid
throw new customException($email);
}
//check for "example" in mail address
if(strpos($email, "example") !== FALSE)
{
throw new Exception("$email is an example e-mail");
}
}

catch (customException $e)
{
echo $e->errorMessage();
}


catch(Exception $e)
{
echo $e->getMessage();
}
?>


Example explained:



The code above tests two conditions and throws an exception if any of the conditions are not met:




  1. The customException() class is created as an extension of the old exception class. This way it inherits all methods and properties from the old exception class


  2. The errorMessage() function is created. This function returns an error message if an e-mail address is invalid


  3. The $email variable is set to a string that is a valid e-mail address, but contains the string "example"


  4. The "try" block is executed and an exception is not thrown on the first condition


  5. The second condition triggers an exception since the e-mail contains the string "example"


  6. The "catch" block catches the exception and displays the correct error message



If there was no customException catch, only the base exception catch, the exception would be handled there






Re-throwing Exceptions



Sometimes, when an exception is thrown, you may wish to handle it differently than the standard way. It is possible to throw an exception a second time within a "catch" block.



A script should hide system errors from users. System errors may be important for the coder, but is of no interest to the user. To make things easier for the user you can re-throw the exception with a user friendly message:



<?php
class customException extends Exception
{
public function errorMessage()
{
//error message
$errorMsg = $this->getMessage().' is not a valid E-Mail address.';
return $errorMsg;
}
}


$email = "someone@example.com";


try
{
try
{
//check for "example" in mail address
if(strpos($email, "example") !== FALSE)
{
//throw exception if email is not valid
throw new Exception($email);
}
}
catch(Exception $e)
{
//re-throw exception
throw new customException($email);
}
}


catch (customException $e)
{
//display custom message
echo $e->errorMessage();
}
?>


Example explained:



The code above tests if the email-address contains the string "example" in it, if it does, the exception is re-thrown:




  1. The customException() class is created as an extension of the old exception class. This way it inherits all methods and properties from the old exception class


  2. The errorMessage() function is created. This function returns an error message if an e-mail address is invalid


  3. The $email variable is set to a string that is a valid e-mail address, but contains the string "example"


  4. The "try" block contains another "try" block to make it possible to re-throw the exception


  5. The exception is triggered since the e-mail contains the string "example"


  6. The "catch" block catches the exception and re-throws a "customException"


  7. The "customException" is caught and displays an error message



If the exception is not caught in its current "try" block, it will search for a catch block on "higher levels".






Set a Top Level Exception Handler



The set_exception_handler() function sets a user-defined function to handle all uncaught exceptions.



<?php
function myException($exception)
{
echo "<b>Exception:</b> " , $exception->getMessage();
}


set_exception_handler('myException');


throw new Exception('Uncaught Exception occurred');
?>


The output of the code above should be something like this:



Exception: Uncaught Exception occurred


In the code above there was no "catch" block. Instead, the top level exception handler triggered. This function should be used to catch uncaught exceptions.






Rules for exceptions




  • Code may be surrounded in a try block, to help catch potential exceptions


  • Each try block or "throw" must have at least one corresponding catch block


  • Multiple catch blocks can be used to catch different classes of exceptions


  • Exceptions can be thrown (or re-thrown) in a catch block within a try block



A simple rule: If you throw something, you have to catch it.

PHP Error Handling

PHP Error Handling

When creating scripts and web applications, error handling is an important part. If your code lacks error checking code, your program may look very unprofessional and you may be open to security risks.

This tutorial contains some of the most common error checking methods in PHP.

We will show different error handling methods:

  • Simple "die()" statements
  • Custom errors and error triggers
  • Error reporting

Basic Error Handling: Using the die() function

The first example shows a simple script that opens a text file:

<?php
$file=fopen("welcome.txt","r");
?>


If the file does not exist you might get an error like this:



Warning: fopen(welcome.txt) [function.fopen]: failed to open stream: 
No such file or directory in C:\webfolder\test.php on line 2


To avoid that the user gets an error message like the one above, we test if the file exist before we try to access it:



<?php
if(!file_exists("welcome.txt"))
{
die("File not found");
}
else
{
$file=fopen("welcome.txt","r");
}
?>


Now if the file does not exist you get an error like this:



File not found


The code above is more efficient than the earlier code, because it uses a simple error handling mechanism to stop the script after the error.



However, simply stopping the script is not always the right way to go. Let's take a look at alternative PHP functions for handling errors.






Creating a Custom Error Handler



Creating a custom error handler is quite simple. We simply create a special function that can be called when an error occurs in PHP.



This function must be able to handle a minimum of two parameters (error level and error message) but can accept up to five parameters (optionally: file, line-number, and the error context):



Syntax



error_function(error_level,error_message,
error_file,error_line,error_context)


Parameter

Description



error_level

Required. Specifies the error report level for the user-defined error. Must be a value number. See table below for possible error report levels



error_message

Required. Specifies the error message for the user-defined error



error_file

Optional. Specifies the filename in which the error occurred



error_line

Optional. Specifies the line number in which the error occurred



error_context

Optional. Specifies an array containing every variable, and their values, in use when the error occurred



Error Report levels



These error report levels are the different types of error the user-defined error handler can be used for:



Value

Constant


Description



2

E_WARNING


Non-fatal run-time errors. Execution of the script is not halted



8

E_NOTICE


Run-time notices. The script found something that might be an error, but could also happen when running a script normally



256

E_USER_ERROR


Fatal user-generated error. This is like an E_ERROR set by the programmer using the PHP function trigger_error()



512

E_USER_WARNING


Non-fatal user-generated warning. This is like an E_WARNING set by the programmer using the PHP function trigger_error()



1024

E_USER_NOTICE


User-generated notice. This is like an E_NOTICE set by the programmer using the PHP function trigger_error()



4096

E_RECOVERABLE_ERROR


Catchable fatal error. This is like an E_ERROR but can be caught by a user defined handle (see also set_error_handler())



8191

E_ALL


All errors and warnings, except level E_STRICT (E_STRICT will be part of E_ALL as of PHP 6.0)



Now lets create a function to handle errors:



function customError($errno, $errstr)
{
echo "<b>Error:</b> [$errno] $errstr<br />";
echo "Ending Script";
die();
}


The code above is a simple error handling function. When it is triggered, it gets the error level and an error message. It then outputs the error level and message and terminates the script.



Now that we have created an error handling function we need to decide when it should be triggered.






Set Error Handler



The default error handler for PHP is the built in error handler. We are going to make the function above the default error handler for the duration of the script.



It is possible to change the error handler to apply for only some errors, that way the script can handle different errors in different ways. However, in this example we are going to use our custom error handler for all errors:



set_error_handler("customError");


Since we want our custom function to handle all errors, the set_error_handler() only needed one parameter, a second parameter could be added to specify an error level.



Example



Testing the error handler by trying to output variable that does not exist:



<?php
//error handler function
function customError($errno, $errstr)
{
echo "<b>Error:</b> [$errno] $errstr";
}


//set error handler
set_error_handler("customError");


//trigger error
echo($test);
?>


The output of the code above should be something like this:



Custom error: [8] Undefined variable: test





Trigger an Error



In a script where users can input data it is useful to trigger errors when an illegal input occurs. In PHP, this is done by the trigger_error() function.



Example



In this example an error occurs if the "test" variable is bigger than "1":



<?php
$test=2;
if ($test>1)
{
trigger_error("Value must be 1 or below");
}
?>


The output of the code above should be something like this:



Notice: Value must be 1 or below
in C:\webfolder\test.php on line 6


An error can be triggered anywhere you wish in a script, and by adding a second parameter, you can specify what error level is triggered.



Possible error types:




  • E_USER_ERROR - Fatal user-generated run-time error. Errors that can not be recovered from. Execution of the script is halted


  • E_USER_WARNING - Non-fatal user-generated run-time warning. Execution of the script is not halted


  • E_USER_NOTICE - Default. User-generated run-time notice. The script found something that might be an error, but could also happen when running a script normally



Example



In this example an E_USER_WARNING occurs if the "test" variable is bigger than "1". If an E_USER_WARNING occurs we will use our custom error handler and end the script:



<?php
//error handler function
function customError($errno, $errstr)
{
echo "<b>Error:</b> [$errno] $errstr<br />";
echo "Ending Script";
die();
}


//set error handler
set_error_handler("customError",E_USER_WARNING);


//trigger error
$test=2;
if ($test>1)
{
trigger_error("Value must be 1 or below",E_USER_WARNING);
}
?>


 


The output of the code above should be something like this:



Error: [512] Value must be 1 or below
Ending Script


Now that we have learned to create our own errors and how to trigger them, lets take a look at error logging.






Error Logging



By default, PHP sends an error log to the servers logging system or a file, depending on how the error_log configuration is set in the php.ini file. By using the error_log() function you can send error logs to a specified file or a remote destination.



Sending errors messages to yourself by e-mail can be a good way of getting notified of specific errors.



Send an Error Message by E-Mail



In the example below we will send an e-mail with an error message and end the script, if a specific error occurs:



<?php
//error handler function
function customError($errno, $errstr)
{
echo "<b>Error:</b> [$errno] $errstr<br />";
echo "Webmaster has been notified";
error_log("Error: [$errno] $errstr",1,
"someone@example.com","From: webmaster@example.com");
}


//set error handler
set_error_handler("customError",E_USER_WARNING);


//trigger error
$test=2;
if ($test>1)
{
trigger_error("Value must be 1 or below",E_USER_WARNING);
}
?>


The output of the code above should be something like this:



Error: [512] Value must be 1 or below
Webmaster has been notified


And the mail received from the code above looks like this:



Error: [512] Value must be 1 or below


This should not be used with all errors. Regular errors should be logged on the server using the default PHP logging system.

PHP Secure E-mails

PHP E-mail Injections

First, look at the PHP code from the previous chapter:

<html>
<body>


<?php
if (isset($_REQUEST['email']))
//if "email" is filled out, send email
{
//send email
$email = $_REQUEST['email'] ;
$subject = $_REQUEST['subject'] ;
$message = $_REQUEST['message'] ;
mail("someone@example.com", "Subject: $subject",
$message, "From: $email" );
echo "Thank you for using our mail form";
}
else
//if "email" is not filled out, display the form
{
echo "<form method='post' action='mailform.php'>
Email: <input name='email' type='text' /><br />
Subject: <input name='subject' type='text' /><br />
Message:<br />
<textarea name='message' rows='15' cols='40'>
</textarea><br />
<input type='submit' />
</form>";
}
?>


</body>
</html>


The problem with the code above is that unauthorized users can insert data into the mail headers via the input form.



What happens if the user adds the following text to the email input field in the form?



someone@example.com%0ACc:person2@example.com
%0ABcc:person3@example.com,person3@example.com,
anotherperson4@example.com,person5@example.com
%0ABTo:person6@example.com


The mail() function puts the text above into the mail headers as usual, and now the header has an extra Cc:, Bcc:, and To: field. When the user clicks the submit button, the e-mail will be sent to all of the addresses above!






PHP Stopping E-mail Injections



The best way to stop e-mail injections is to validate the input.



The code below is the same as in the previous chapter, but now we have added an input validator that checks the email field in the form:



<html>
<body>
<?php
function spamcheck($field)
{
//filter_var() sanitizes the e-mail
//address using FILTER_SANITIZE_EMAIL
$field=filter_var($field, FILTER_SANITIZE_EMAIL);

//filter_var() validates the e-mail
//address using FILTER_VALIDATE_EMAIL
if(filter_var($field, FILTER_VALIDATE_EMAIL))
{
return TRUE;
}
else
{
return FALSE;
}
}


if (isset($_REQUEST['email']))
{//if "email" is filled out, proceed


  //check if the email address is invalid
$mailcheck = spamcheck($_REQUEST['email']);
if ($mailcheck==FALSE)
{
echo "Invalid input";
}
else
{//send email
$email = $_REQUEST['email'] ;
$subject = $_REQUEST['subject'] ;
$message = $_REQUEST['message'] ;
mail("someone@example.com", "Subject: $subject",
$message, "From: $email" );
echo "Thank you for using our mail form";
}
}
else
{//if "email" is not filled out, display the form
echo "<form method='post' action='mailform.php'>
Email: <input name='email' type='text' /><br />
Subject: <input name='subject' type='text' /><br />
Message:<br />
<textarea name='message' rows='15' cols='40'>
</textarea><br />
<input type='submit' />
</form>";
}
?>


</body>
</html>


In the code above we use PHP filters to validate input:




  • The FILTER_SANITIZE_EMAIL filter removes all illegal e-mail characters from a string


  • The FILTER_VALIDATE_EMAIL filter validates value as an e-mail address



You can read more about filters in our PHP Filter chapter.

PHP Sending E-mails

The PHP mail() Function

The PHP mail() function is used to send emails from inside a script.

Syntax

mail(to,subject,message,headers,parameters)


Parameter

Description



to

Required. Specifies the receiver / receivers of the email



subject

Required. Specifies the subject of the email. Note: This parameter cannot contain any newline characters



message

Required. Defines the message to be sent. Each line should be separated with a LF (\n). Lines should not exceed 70 characters



headers

Optional. Specifies additional headers, like From, Cc, and Bcc. The additional headers should be separated with a CRLF (\r\n)



parameters

Optional. Specifies an additional parameter to the sendmail program



Note: For the mail functions to be available, PHP requires an installed and working email system. The program to be used is defined by the configuration settings in the php.ini file. Read more in our PHP Mail reference.






PHP Simple E-Mail



The simplest way to send an email with PHP is to send a text email.



In the example below we first declare the variables ($to, $subject, $message, $from, $headers), then we use the variables in the mail() function to send an e-mail:



<?php


$to = "someone@example.com";
$subject = "Test mail";
$message = "Hello! This is a simple email message.";
$from = "someonelse@example.com";
$headers = "From: $from";
mail($to,$subject,$message,$headers);
echo "Mail Sent.";


?>





PHP Mail Form



With PHP, you can create a feedback-form on your website. The example below sends a text message to a specified e-mail address:



<html>
<body>


<?php
if (isset($_REQUEST['email']))
//if "email" is filled out, send email
{
//send email
$email = $_REQUEST['email'] ;
$subject = $_REQUEST['subject'] ;
$message = $_REQUEST['message'] ;
mail( "someone@example.com", "Subject: $subject",
$message, "From: $email" );
echo "Thank you for using our mail form";
}
else
//if "email" is not filled out, display the form
{
echo "<form method='post' action='mailform.php'>
Email: <input name='email' type='text' /><br />
Subject: <input name='subject' type='text' /><br />
Message:<br />
<textarea name='message' rows='15' cols='40'>
</textarea><br />
<input type='submit' />
</form>";
}
?>


</body>
</html>


This is how the example above works:




  • First, check if the email input field is filled out


  • If it is not set (like when the page is first visited); output the HTML form


  • If it is set (after the form is filled out); send the email from the form


  • When submit is pressed after the form is filled out, the page reloads, sees that the email input is set, and sends the email



Note: This is the simplest way to send e-mail, but it is not secure. In the next chapter of this tutorial you can read more about vulnerabilities in e-mail scripts, and how to validate user input to make it more secure.






PHP Mail Reference



For more information about the PHP mail() function, visit our PHP Mail Reference.

PHP Sessions

PHP Session Variables

When you are working with an application, you open it, do some changes and then you close it. This is much like a Session. The computer knows who you are. It knows when you start the application and when you end. But on the internet there is one problem: the web server does not know who you are and what you do because the HTTP address doesn't maintain state.

A PHP session solves this problem by allowing you to store user information on the server for later use (i.e. username, shopping items, etc). However, session information is temporary and will be deleted after the user has left the website. If you need a permanent storage you may want to store the data in a database.

Sessions work by creating a unique id (UID) for each visitor and store variables based on this UID. The UID is either stored in a cookie or is propagated in the URL.


Starting a PHP Session

Before you can store user information in your PHP session, you must first start up the session.

Note: The session_start() function must appear BEFORE the <html> tag:

<?php session_start(); ?>


<html>
<body>


</body>
</html>


The code above will register the user's session with the server, allow you to start saving user information, and assign a UID for that user's session.






Storing a Session Variable



The correct way to store and retrieve session variables is to use the PHP $_SESSION variable:



<?php
session_start();
// store session data
$_SESSION['views']=1;
?>


<html>
<body>


<?php
//retrieve session data
echo "Pageviews=". $_SESSION['views'];
?>


</body>
</html>


Output:



Pageviews=1


In the example below, we create a simple page-views counter. The isset() function checks if the "views" variable has already been set. If "views" has been set, we can increment our counter. If "views" doesn't exist, we create a "views" variable, and set it to 1:



<?php

session_start();


if(isset($_SESSION['views']))
$_SESSION['views']=$_SESSION['views']+1;

else
$_SESSION['views']=1;
echo "Views=". $_SESSION['views'];
?>





Destroying a Session



If you wish to delete some session data, you can use the unset() or the session_destroy() function.



The unset() function is used to free the specified session variable:



<?php
unset($_SESSION['views']);
?>


You can also completely destroy the session by calling the session_destroy() function:



<?php
session_destroy();
?>


Note: session_destroy() will reset your session and you will lose all your stored session data.

PHP Cookies

What is a Cookie?

A cookie is often used to identify a user. A cookie is a small file that the server embeds on the user's computer. Each time the same computer requests a page with a browser, it will send the cookie too. With PHP, you can both create and retrieve cookie values.


How to Create a Cookie?

The setcookie() function is used to set a cookie.

Note: The setcookie() function must appear BEFORE the <html> tag.

Syntax
setcookie(name, value, expire, path, domain);


Example


In the example below, we will create a cookie named "user" and assign the value "Alex Porter" to it. We also specify that the cookie should expire after one hour:



<?php 
setcookie("user", "Alex Porter", time()+3600);
?>


<html>
<body>


</body>
</html>


Note: The value of the cookie is automatically URLencoded when sending the cookie, and automatically decoded when received (to prevent URLencoding, use setrawcookie() instead).






How to Retrieve a Cookie Value?



The PHP $_COOKIE variable is used to retrieve a cookie value.

In the example below, we retrieve the value of the cookie named "user" and display it on a page:



<?php
// Print a cookie
echo $_COOKIE["user"];


// A way to view all cookies
print_r($_COOKIE);
?>


In the following example we use the isset() function to find out if a cookie has been set:



<html>
<body>


<?php
if (isset($_COOKIE["user"]))
echo "Welcome " . $_COOKIE["user"] . "!<br />";
else
echo "Welcome guest!<br />";
?>


</body>
</html>





How to Delete a Cookie?



When deleting a cookie you should assure that the expiration date is in the past.



Delete example:



<?php 
// set the expiration date to one hour ago
setcookie("user", "", time()-3600);
?>





What if a Browser Does NOT Support Cookies?



If your application deals with browsers that do not support cookies, you will have to use other methods to pass information from one page to another in your application. One method is to pass the data through forms (forms and user input are described earlier in this tutorial).



The form below passes the user input to "welcome.php" when the user clicks on the "Submit" button:



<html>
<body>


<form action="welcome.php" method="post">
Name: <input type="text" name="name" />
Age: <input type="text" name="age" />
<input type="submit" />
</form>


</body>
</html>


Retrieve the values in the "welcome.php" file like this:



<html>
<body>


Welcome <?php echo $_POST["name"]; ?>.<br />
You are <?php echo $_POST["age"]; ?> years old.


</body>
</html>

PHP File Upload

Create an Upload-File Form

To allow users to upload files from a form can be very useful.

Look at the following HTML form for uploading files:

<html>
<body>


<form action="upload_file.php" method="post"
enctype="multipart/form-data">
<label for="file">Filename:</label>
<input type="file" name="file" id="file" />
<br />
<input type="submit" name="submit" value="Submit" />
</form>


</body>
</html>


Notice the following about the HTML form above:




  • The enctype attribute of the <form> tag specifies which content-type to use when submitting the form. "multipart/form-data" is used when a form requires binary data, like the contents of a file, to be uploaded


  • The type="file" attribute of the <input> tag specifies that the input should be processed as a file. For example, when viewed in a browser, there will be a browse-button next to the input field



Note: Allowing users to upload files is a big security risk. Only permit trusted users to perform file uploads.






Create The Upload Script



The "upload_file.php" file contains the code for uploading a file:



<?php
if ($_FILES["file"]["error"] > 0)
{
echo "Error: " . $_FILES["file"]["error"] . "<br />";
}
else
{
echo "Upload: " . $_FILES["file"]["name"] . "<br />";
echo "Type: " . $_FILES["file"]["type"] . "<br />";
echo "Size: " . ($_FILES["file"]["size"] / 1024) . " Kb<br />";
echo "Stored in: " . $_FILES["file"]["tmp_name"];
}
?>


By using the global PHP $_FILES array you can upload files from a client computer to the remote server.



The first parameter is the form's input name and the second index can be either "name", "type", "size", "tmp_name" or "error". Like this:




  • $_FILES["file"]["name"] - the name of the uploaded file


  • $_FILES["file"]["type"] - the type of the uploaded file


  • $_FILES["file"]["size"] - the size in bytes of the uploaded file


  • $_FILES["file"]["tmp_name"] - the name of the temporary copy of the file stored on the server


  • $_FILES["file"]["error"] - the error code resulting from the file upload



This is a very simple way of uploading files. For security reasons, you should add restrictions on what the user is allowed to upload.






Restrictions on Upload



In this script we add some restrictions to the file upload. The user may only upload .gif or .jpeg files and the file size must be under 20 kb:



<?php


if ((($_FILES["file"]["type"] == "image/gif")
|| ($_FILES["file"]["type"] == "image/jpeg")
|| ($_FILES["file"]["type"] == "image/pjpeg"))
&& ($_FILES["file"]["size"] < 20000))
{
if ($_FILES["file"]["error"] > 0)
{
echo "Error: " . $_FILES["file"]["error"] . "<br />";
}
else
{
echo "Upload: " . $_FILES["file"]["name"] . "<br />";
echo "Type: " . $_FILES["file"]["type"] . "<br />";
echo "Size: " . ($_FILES["file"]["size"] / 1024) . " Kb<br />";
echo "Stored in: " . $_FILES["file"]["tmp_name"];
}
}
else
{
echo "Invalid file";
}


?>


Note: For IE to recognize jpg files the type must be pjpeg, for FireFox it must be jpeg.






Saving the Uploaded File



The examples above create a temporary copy of the uploaded files in the PHP temp folder on the server.



The temporary copied files disappears when the script ends. To store the uploaded file we need to copy it to a different location:



<?php
if ((($_FILES["file"]["type"] == "image/gif")
|| ($_FILES["file"]["type"] == "image/jpeg")
|| ($_FILES["file"]["type"] == "image/pjpeg"))
&& ($_FILES["file"]["size"] < 20000))
{
if ($_FILES["file"]["error"] > 0)
{
echo "Return Code: " . $_FILES["file"]["error"] . "<br />";
}
else
{
echo "Upload: " . $_FILES["file"]["name"] . "<br />";
echo "Type: " . $_FILES["file"]["type"] . "<br />";
echo "Size: " . ($_FILES["file"]["size"] / 1024) . " Kb<br />";
echo "Temp file: " . $_FILES["file"]["tmp_name"] . "<br />";


    if (file_exists("upload/" . $_FILES["file"]["name"]))
{
echo $_FILES["file"]["name"] . " already exists. ";
}
else
{
move_uploaded_file($_FILES["file"]["tmp_name"],
"upload/" . $_FILES["file"]["name"]);
echo "Stored in: " . "upload/" . $_FILES["file"]["name"];
}
}
}
else
{
echo "Invalid file";
}
?>


The script above checks if the file already exists, if it does not, it copies the file to the specified folder.



Note: This example saves the file to a new folder called "upload"

PHP File Handling

Opening a File

The fopen() function is used to open files in PHP.

The first parameter of this function contains the name of the file to be opened and the second parameter specifies in which mode the file should be opened:

<html>
<body>


<?php
$file=fopen("welcome.txt","r");
?>


</body>
</html>


The file may be opened in one of the following modes:



Modes

Description



r

Read only. Starts at the beginning of the file



r+

Read/Write. Starts at the beginning of the file



w

Write only. Opens and clears the contents of file; or creates a new file if it doesn't exist



w+

Read/Write. Opens and clears the contents of file; or creates a new file if it doesn't exist



a

Append. Opens and writes to the end of the file or creates a new file if it doesn't exist



a+

Read/Append. Preserves file content by writing to the end of the file



x

Write only. Creates a new file. Returns FALSE and an error if file already exists



x+

Read/Write. Creates a new file. Returns FALSE and an error if file already exists



Note: If the fopen() function is unable to open the specified file, it returns 0 (false).



Example


The following example generates a message if the fopen() function is unable to open the specified file:



<html>
<body>


<?php
$file=fopen("welcome.txt","r") or exit("Unable to open file!");
?>


</body>
</html>





Closing a File



The fclose() function is used to close an open file:



<?php
$file = fopen("test.txt","r");


//some code to be executed


fclose($file);
?>





Check End-of-file



The feof() function checks if the "end-of-file" (EOF) has been reached.

The feof() function is useful for looping through data of unknown length.



Note: You cannot read from files opened in w, a, and x mode!



if (feof($file)) echo "End of file";





Reading a File Line by Line



The fgets() function is used to read a single line from a file.



Note: After a call to this function the file pointer has moved to the next line.



Example


The example below reads a file line by line, until the end of file is reached:



<?php
$file = fopen("welcome.txt", "r") or exit("Unable to open file!");
//Output a line of the file until the end is reached
while(!feof($file))
{
echo fgets($file). "<br />";
}
fclose($file);
?>





Reading a File Character by Character



The fgetc() function is used to read a single character from a file.



Note: After a call to this function the file pointer moves to the next character.



Example


The example below reads a file character by character, until the end of file is reached:



<?php
$file=fopen("welcome.txt","r") or exit("Unable to open file!");
while (!feof($file))
{
echo fgetc($file);
}
fclose($file);
?>





PHP Filesystem Reference



For a full reference of the PHP filesystem functions, visit our PHP Filesystem Reference.

PHP Include File

Server Side Includes

You can insert the content of a file into a PHP file before the server executes it, with the include() or require() function. The two functions are identical in every way, except how they handle errors. The include() function generates a warning (but the script will continue execution) while the require() function generates a fatal error (and the script execution will stop after the error).

These two functions are used to create functions, headers, footers, or elements that can be reused on multiple pages.

This can save the developer a considerable amount of time. This means that you can create a standard header or menu file that you want all your web pages to include. When the header needs to be updated, you can only update this one include file, or when you add a new page to your site, you can simply change the menu file (instead of updating the links on all web pages).


The include() Function

The include() function takes all the text in a specified file and copies it into the file that uses the include function.

Example 1

Assume that you have a standard header file, called "header.php". To include the header file in a page, use the include() function, like this:

<html>
<body>


<?php include("header.php"); ?>


<h1>Welcome to my home page</h1>


<p>Some text</p>


</body>
</html>


Example 2


Now, let's assume we have a standard menu file that should be used on all pages (include files usually have a ".php" extension). Look at the "menu.php" file below:



<html>
<body>


<a href="http://www.w3schools.com/default.php">Home</a> |
<a href="http://www.w3schools.com/about.php">About Us</a> |
<a href="http://www.w3schools.com/contact.php">Contact Us</a>


The three files, "default.php", "about.php", and "contact.php" should all include the "menu.php" file. Here is the code in "default.php":



<?php include("menu.php"); ?>


<h1>Welcome to my home page</h1>


<p>Some text</p>


</body>
</html>


If you look at the source code of the "default.php" in a browser, it will look something like this:



<html>
<body>
<a href="default.php">Home</a> |
<a href="about.php">About Us</a> |
<a href="contact.php">Contact Us</a>
<h1>Welcome to my home page</h1>
<p>Some text</p>
</body>
</html>


And, of course, we would have to do the same thing for "about.php" and "contact.php". By using include files, you simply have to update the text in the "menu.php" file if you decide to rename or change the order of the links or add another web page to the site.






The require() Function



The require() function is identical to include(), except that it handles errors differently.



The include() function generates a warning (but the script will continue execution) while the require() function generates a fatal error (and the script execution will stop after the error).



If you include a file with the include() function and an error occurs, you might get an error message like the one below.



PHP code:



<html>
<body>

<?php
include("wrongFile.php");
echo "Hello World!";
?>

</body>
</html>


Error message:



Warning: include(wrongFile.php) [function.include]:
failed to open stream:
No such file or directory in C:\home\website\test.php on line 5


Warning: include() [function.include]:
Failed opening 'wrongFile.php' for inclusion
(include_path='.;C:\php5\pear')
in C:\home\website\test.php on line 5


Hello World!


Notice that the echo statement is still executed! This is because a Warning does not stop the script execution.



Now, let's run the same example with the require() function.



PHP code:



<html>
<body>

<?php
require("wrongFile.php");
echo "Hello World!";
?>

</body>
</html>


Error message:



Warning: require(wrongFile.php) [function.require]:
failed to open stream:
No such file or directory in C:\home\website\test.php on line 5


Fatal error: require() [function.require]:
Failed opening required 'wrongFile.php'
(include_path='.;C:\php5\pear')
in C:\home\website\test.php on line 5


The echo statement was not executed because the script execution stopped after the fatal error.



It is recommended to use the require() function instead of include(), because scripts should not continue executing if files are missing or misnamed.

PHP Date()

The PHP Date() Function

The PHP date() function formats a timestamp to a more readable date and time.

Syntax
date(format,timestamp)


Parameter

Description



format

Required. Specifies the format of the timestamp



timestamp

Optional. Specifies a timestamp. Default is the current date and time (as a timestamp)






PHP Date - What is a Timestamp?



A timestamp is the number of seconds since January 1, 1970 at 00:00:00 GMT. This is also known as the Unix Timestamp.






PHP Date - Format the Date



The first parameter in the date() function specifies how to format the date/time. It uses letters to represent date and time formats. Here are some of the letters that can be used:




  • d - The day of the month (01-31)


  • m - The current month, as a number (01-12)


  • Y - The current year in four digits



An overview of all the letters that can be used in the format parameter, can be found in our PHP Date reference.



Other characters, like"/", ".", or "-" can also be inserted between the letters to add additional formatting:



<?php
echo date("Y/m/d");
echo "<br />";
echo date("Y.m.d");
echo "<br />";
echo date("Y-m-d");
?>


The output of the code above could be something like this:



2006/07/11
2006.07.11
2006-07-11





PHP Date - Adding a Timestamp



The second parameter in the date() function specifies a timestamp. This parameter is optional. If you do not supply a timestamp, the current time will be used.



In our next example we will use the mktime() function to create a timestamp for tomorrow.



The mktime() function returns the Unix timestamp for a specified date.



Syntax


mktime(hour,minute,second,month,day,year,is_dst)


To go one day in the future we simply add one to the day argument of mktime():



<?php
$tomorrow = mktime(0,0,0,date("m"),date("d")+1,date("Y"));
echo "Tomorrow is ".date("Y/m/d", $tomorrow);
?>


The output of the code above could be something like this:



Tomorrow is 2006/07/12





PHP Date - Reference



For more information about all the PHP date functions, please visit our PHP Date Reference.

PHP $_POST

The $_POST Variable

The $_POST variable is an array of variable names and values sent by the HTTP POST method.

The $_POST variable is used to collect values from a form with method="post". Information sent from a form with the POST method is invisible to others and has no limits on the amount of information to send.

Example
<form action="welcome.php" method="post">
Enter your name: <input type="text" name="name" />
Enter your age: <input type="text" name="age" />
<input type="submit" />
</form>


When the user clicks the "Submit" button, the URL will not contain any form data, and will look something like this:



http://www.w3schools.com/welcome.php


The "welcome.php" file can now use the $_POST variable to catch the form data (notice that the names of the form fields will automatically be the ID keys in the $_POST array):



Welcome <?php echo $_POST["name"]; ?>.<br />
You are <?php echo $_POST["age"]; ?> years old!





Why use $_POST?




  • Variables sent with HTTP POST are not shown in the URL


  • Variables have no length limit



However, because the variables are not displayed in the URL, it is not possible to bookmark the page.






The $_REQUEST Variable



The PHP $_REQUEST variable contains the contents of both $_GET, $_POST, and $_COOKIE.



The PHP $_REQUEST variable can be used to get the result from form data sent with both the GET and POST methods.



Example


Welcome <?php echo $_REQUEST["name"]; ?>.<br />
You are <?php echo $_REQUEST["age"]; ?> years old!