The SplAutoloader Interface

Overview

While any valid PHP callback may be registered with spl_autoload_register(), Zend Framework autoloaders often provide more flexibility by being stateful and allowing configuration. To provide a common interface, Zend Framework 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, simply create a class implementing the SplAutoloader interface (you may review the methods defined in the Methods section). As a simple 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 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;
            }
        }
        return $this;
    }

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

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

To use this ModifiedIncludePathAutoloader from the previous example:

$options = array(
   '/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

Initialize and configure an autoloader __construct($options = null)

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

setOptions

Configure the autoloader state setOptions($options)

setOptions() 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. Additionally, it is recommended that the method return the autoloader instance in order to implement a fluent interface.

autoload

Attempt to resolve a class name to the file defining it autoload($classname)

autoload() 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 the autoloader with the SPL autoloader register()

register() 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(array($this, 'autoload'));
}

Examples

Please see the Quick Start for a complete example.