The SplAutoloader Interface

While any valid PHP callback may be registered with spl_autoload_register(), the autoloaders zend-loader provides offer more flexibility by being stateful and allowing configuration. To provide a common interface for such autoloaders, zend-loader provides the SplAutoloader interface.

Objects implementing this interface provide a standard mechanism for configuration, a method that may be invoked to attempt to load a class, and a method for registering with the SPL autoloading mechanism.

Quick Start

To create your own autoloading mechanism, create a class implementing the SplAutoloader interface (you may review the methods defined in the methods section). As an example, consider the following autoloader, which will look for a class file named after the class within a list of registered directories.

namespace Custom;

use InvalidArgumentException;
use Traversable;
use Zend\Loader\SplAutoloader;

class ModifiedIncludePathAutoloader implements SplAutoloader
{
    protected $paths = array();

    public function __construct($options = null)
    {
        if (null !== $options) {
            $this->setOptions($options);
        }
    }

    public function setOptions($options)
    {
        if (! is_array($options) && ! $options instanceof Traversable) {
            throw new InvalidArgumentException();
        }

        foreach ($options as $path) {
            if (! in_array($path, $this->paths)) {
                $this->paths[] = $path;
            }
        }
    }

    public function autoload($classname)
    {
        $filename = $classname . '.php';
        foreach ($this->paths as $path) {
            $test = sprintf('%s/%s', $path, $filename);
            if (file_exists($test)) {
                return include($test);
            }
        }
        return false;
    }

    public function register()
    {
        spl_autoload_register([$this, 'autoload']);
    }
}

To use this ModifiedIncludePathAutoloader from the previous example:

$options = [
   '/path/one',
   '/path/two',
];
$autoloader = new Custom\ModifiedIncludePathAutoloader($options);
$autoloader->register();

Configuration Options

This component defines no configuration options, as it is an interface.

Available Methods

__construct

__construct($options = null) : void

Autoloader constructors should optionally receive configuration. Typically, if received, these will be passed to the setOptions() method to process.

setOptions

setOptions(array|Traversable $options) : void

Used to configure the autoloader. Typically, it should expect either an array or a Traversable object, though validation of the options is left to implementation.

autoload

autoload(string $class) : false|string

This method should be used to resolve a class name to the file defining it. When a positive match is found, return the class name; otherwise, return a boolean false.

register

register() : void

Should be used to register the autoloader instance with spl_autoload_register(). Invariably, the method should look like the following:

public function register()
{
    spl_autoload_register([$this, 'autoload']);
}