PHP Autoloading Primer Autoloading as part of a framework solution


// autoload.php
spl_autoload_register(function ($class) {
    require_once "$class.php";

// Animal.php
class Animal {
    public function eats($food) {
         echo "Yum, $food!";

// Ruminant.php
class Ruminant extends Animal {
    public function eats($food) {
        if ('grass' === $food) {
        } else {
            echo "Yuck, $food!";

// Cow.php
class Cow extends Ruminant {

// pasture.php
require 'autoload.php';
$animal = new Cow;

Thanks to our generic autoloader, we have access to any class that follows our autoloader naming convention. In this example, our convention is simple: the desired class must have a file in the same directory named for the class and ending in ".php". Notice that the class name exactly matches the file name.

Without autoloading, we would have to manually require base classes. If we built an entire zoo of animals, we'd have thousands of require statements that could more easily be replaced with a single autoloader.

In the final analysis, PHP autoloading is a mechanism to help you write less mechanical code so you can focus on solving business problems. All you have to do is define a strategy that maps class name to file name. You can roll your own autoloading strategy, as done here. Or, you can use any of the standard ones the PHP community has adopted: PSR-0 or PSR-4. Or, you can use composer to generically define and manage these dependencies.