PHP Autoloading classes

At first I find autoloading a tricky thing to do, the way Composer does and frameworks but not anymore. Today I will share the secret on how classes are loaded on demand.

You can actually gain access to a class by including them in your bootstrap file but what if we have a lot of files? This time we will do autoloading and bootstrap only the files needed. i.e.

index.php

require 'bootstrap.php';

// initialized class here and it will be autoloaded
$foo = new Foo;
$bar = new Bar;

Let's not imagine, but let's say this will be our working directory. Our target classes to be autolaoded will be under the services folder.

/project
	/services
		Foo.php
		Bar.php
		...
	bootstrap.php
	index.php

Let's now reveal our bootstrap.php file.

bootstrap.php

spl_autoload_register(function($class) {
	if(file_exists($path = __DIR__.'/services/'.$class.'.php')) 
	{
		require_once $path;
		return true;
	}
	return false;
});

You can do your implementation within the callable but in our example our target directory is the services folder where our classes is located.

spl_autoload_register accepts a callable as the first parameter.

/**
 * @param callable $autoload_function 
 * @param bool     $throw 	whether to throw exceptions when the autoload_function cannot be registered.
 * @param bool     $prepend 	whether to prepend the autoloader on the autoload stack
 */
spl_autoload_register(callable $autoload_function, $throw = true, $prepend = false)

Another way to do autoloading is the __autoload() function. We can achieve the same as above with the following code.

bootstrap.php

function __autoload(string $class) {
	if(file_exists($path =  __DIR__.'/services/'.$class.'.php')) {
		require_once $path;
	}
}

By default spl_autoload_register replace the engine cache for __autoload() function. So if you definde a spl_autoload_register then it will be use.

The use of __autoload() is discourage and may be depreciated or remove later on in favor of spl_autoload_register because the later provides a more flexible alternative for autoloading classes.

Let me know your comments!