Saturday, August 16, 2008

PHP Functions

PHP Functions

In this tutorial we will show you how to create your own functions.

For a reference and examples of the built-in functions, please visit our PHP Reference.


Create a PHP Function

A function is a block of code that can be executed whenever we need it.
Creating PHP functions:

  • All functions start with the word "function()"
  • Name the function - It should be possible to understand what the function does by its name. The name can start with a letter or underscore (not a number)
  • Add a "{"  - The function code starts after the opening curly brace
  • Insert the function code
  • Add a "}"  - The function is finished by a closing curly brace
Example

A simple function that writes my name when it is called:

<html>
<body>


<?php
function writeMyName()
{
echo "Kai Jim Refsnes";
}


writeMyName();
?>


</body>
</html>





Use a PHP Function



Now we will use the function in a PHP script:



<html>
<body>


<?php
function writeMyName()
{
echo "Kai Jim Refsnes";
}


echo "Hello world!<br />";
echo "My name is ";
writeMyName();
echo ".<br />That's right, ";
writeMyName();
echo " is my name.";
?>


</body>
</html>


The output of the code above will be:



Hello world!
My name is Kai Jim Refsnes.
That's right, Kai Jim Refsnes is my name.





PHP Functions - Adding parameters



Our first function (writeMyName()) is a very simple function. It only writes a static string.



To add more functionality to a function, we can add parameters. A parameter is just like a variable.



You may have noticed the parentheses after the function name, like: writeMyName(). The parameters are specified inside the parentheses.



Example 1


The following example will write different first names, but the same last name:



<html>
<body>


<?php
function writeMyName($fname)
{
echo $fname . " Refsnes.<br />";
}


echo "My name is ";
writeMyName("Kai Jim");


echo "My name is ";
writeMyName("Hege");


echo "My name is ";
writeMyName("Stale");
?>


</body>
</html>


The output of the code above will be:



My name is Kai Jim Refsnes.
My name is Hege Refsnes.
My name is Stale Refsnes.


Example 2


The following function has two parameters:



<html>
<body>


<?php
function writeMyName($fname,$punctuation)
{
echo $fname . " Refsnes" . $punctuation . "<br />";
}


echo "My name is ";
writeMyName("Kai Jim",".");


echo "My name is ";
writeMyName("Hege","!");


echo "My name is ";
writeMyName("Ståle","...");
?>


</body>
</html>


The output of the code above will be:



My name is Kai Jim Refsnes.
My name is Hege Refsnes!
My name is Ståle Refsnes...





PHP Functions - Return values



Functions can also be used to return values.



Example


<html>
<body>


<?php
function add($x,$y)
{
$total = $x + $y;
return $total;
}


echo "1 + 16 = " . add(1,16);
?>


</body>
</html>


The output of the code above will be:



1 + 16 = 17

No comments: