Question

The spl_autoload_register() function can be used with 3 types of callbacks: functions, static methods and regular methods. Are there any advantages/disadvantages for these 3 types compared to each other?

Answer 1

Not really any major differences.

A closure (defined like the following (PHP 5.3+ only)) can never be unregistered, unless it is saved to a variable:

spl_autoload_register(function($class) { ... });

A static method can actually auto load the static class before running its autoloader

spl_autoload_register(function($class) {
    if ($class === 'AutoLoader') {
        var_dump('Auto loading AutoLoader');
        class AutoLoader {
            public static function autoload($class) {
                var_dump(__CLASS__ . ' is loading: ' . $class);
            }
        }
    }
});

spl_autoload_register('AutoLoader::autoload');

Test::func();

// 'Auto loading AutoLoader'
// 'AutoLoader is loading: Test'

Although, I dont know why you would want to do that.

Static calls are easier to unregister though.

Either way you should follow the PSR0 auto loading standards: https://gist.github.com/221634