spl_autoload_register

Register given function as __autoload() implementation

&reftitle.description; `bool` `spl_autoload_register` ``callable``null```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.

&reftitle.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.

  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.

&reftitle.returnvalues;

&return.success;

&reftitle.changelog;

&Version; | &Description;
8.0.0 | `callback` is now nullable.

&reftitle.examples;

### `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';
    });

    ?>

### `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;

    ?>

&example.outputs.similar;

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

### 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');

    ?>

&example.outputs;

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

&reftitle.seealso;

- `__autoload`