Autoloading Classes

Update: Times change, now that PHP 5.3 has namespaces, check out the PSR-0 Standard for autoloading. Hari K T wrote a great introduction to some of the benefits over at PHPMaster.

For those PHP coders out there that are starting to use OOP, if you don’t know about the autoload function, read on.

It is simple to instantiate objects anywhere in your code without having to worry if the class has been included by using the __autoload function. When working with autoload you must have a naming convention that you will stick with. Throughout this example I will provide my naming conventions, but feel free to modify it to suit your style.

Create a directory in your webroot called “lib”. This will contain all your class files as well as an include file which we will be creating shortly. Name all your class files with the exact same name as the class except in lowercase letters, followed by “.class.php”. So for your Product class it would be named, “product.class.php”.

Now create a file called include.php in your lib directory with the following code:

function __autoload($name){
	$path = pathinfo(__FILE__);
	$name = strtolower($name);
	include_once("{$path['dirname']}/{$name}.class.php");
}

Create an index.php file in your webroot and include the lib/include.php file you just created. You can now instantiate any object that is available to you in your library of classes without having to manually include each class. Cool, huh?!

include_once('lib/include.php');
$object = new Class();