SPL Functions
PHP Manual

spl_autoload_register

Register given function as __autoload() implementation

Description

bool spl_autoload_register(callablenull $callback = null, bool $throw = true, bool $prepend = false)

Register a function with the spl provided __autoload queue. If the queue is not yet activated it will be activated.

If your code has an existing __autoload function then this function must be explicitly registered on the __autoload queue. This is because spl_autoload_register will effectively replace the engine cache for the __autoload function by either spl_autoload or spl_autoload_call.

If there must be multiple autoload functions, spl_autoload_register allows for this. It effectively creates a queue of autoload functions, and runs through each of them in the order they are defined. By contrast, __autoload may only be defined once.

Parameters

callback

The autoload function being registered. If null, then the default implementation of spl_autoload will be registered.

void callback(string $class)

The class will not contain the leading backslash of a fully-qualified identifier.

throw

This parameter specifies whether spl_autoload_register should throw exceptions when the callback cannot be registered.

Warning

This parameter is ignored as of PHP 8.0.0, and a notice will be emitted if set to false. spl_autoload_register will now always throw a TypeError on invalid arguments.

prepend

If true, spl_autoload_register will prepend the autoloader on the autoload queue instead of appending it.

Return Values

Returns true on success or false on failure.

Changelog

Version Description
8.0.0 callback is now nullable.

Examples

Example #1 spl_autoload_register as a replacement for an __autoload function

<?php

// function __autoload($class) {
//     include 'classes/' . $class . '.class.php';
// }

function my_autoloader($class) {
    include 'classes/' . $class . '.class.php';
}

spl_autoload_register('my_autoloader');

// Or, using an anonymous function
spl_autoload_register(function ($class) {
    include 'classes/' . $class . '.class.php';
});

?>

Example #2 spl_autoload_register example where the class is not loaded

<?php

namespace Foobar;

class Foo {
    static public function test($class) {
        print '[['. $class .']]';
    }
}

spl_autoload_register(__NAMESPACE__ .'\Foo::test');

new InexistentClass;

?>

The above example will output something similar to:

[[Foobar\InexistentClass]]
Fatal error: Class 'Foobar\InexistentClass' not found in ...

Example #3 The identifier will be provided without the leading backslash

<?php

spl_autoload_register(static function ($class) {
    var_dump($class);
});

class_exists('RelativeName');
class_exists('RelativeName\\WithNamespace');
class_exists('\\AbsoluteName');
class_exists('\\AbsoluteName\\WithNamespace');

?>

The above example will output:

string(12) "RelativeName"
string(26) "RelativeName\WithNamespace"
string(12) "AbsoluteName"
string(26) "AbsoluteName\WithNamespace"

See Also

  • __autoload