The ClassMapAutoloader

Overview

The ClassMapAutoloader is designed with performance in mind. The idea behind it is simple: when asked to load a class, see if it’s in the map, and, if so, load the file associated with the class in the map. This avoids unnecessary filesystem operations, and can also ensure the autoloader “plays nice” with opcode caches and PHP’s realpath cache.

Zend Framework provides a tool for generating these class maps; you can find it in bin/classmap_generator.php of the distribution. Full documentation of this is provided in the Class Map generator section.

Quick Start

The first step is to generate a class map file. You may run this over any directory containing source code anywhere underneath it.

php classmap_generator.php Some/Directory/

This will create a file named Some/Directory/autoload_classmap.php, which is a PHP file returning an associative array that represents the class map.

Within your code, you will now instantiate the ClassMapAutoloader, and provide it the location of the map.

// This example assumes ZF is on your include_path.
// You could also load the autoloader class from a path relative to the
// current script, or via an absolute path.
require_once 'Zend/Loader/ClassMapAutoloader.php';
$loader = new Zend\Loader\ClassMapAutoloader();

// Register the class map:
$loader->registerAutoloadMap('Some/Directory/autoload_classmap.php');

// Register with spl_autoload:
$loader->register();

At this point, you may now use any classes referenced in your class map.

Configuration Options

The ClassMapAutoloader defines the following options.

ClassMapAutoloader Options

$options

The ClassMapAutoloader expects an array of options, where each option is either a filename referencing a class map, or an associative array of class name/filename pairs.

As an example:

// Configuration defining both a file-based class map, and an array map
$config = array(
    __DIR__ . '/library/autoloader_classmap.php', // file-based class map
    array(                              // array class map
        'Application\Bootstrap' => __DIR__ . '/application/Bootstrap.php',
        'Test\Bootstrap'        => __DIR__ . '/tests/Bootstrap.php',
    ),
);

Available Methods

__construct

Initialize and configure the object __construct($options = null)

Constructor Used during instantiation of the object. Optionally, pass options, which may be either an array or Traversable object; this argument will be passed to setOptions().

setOptions

Configure the autoloader setOptions($options)

setOptions() Configures the state of the autoloader, including registering class maps. Expects an array or Traversable object; the argument will be passed to registerAutoloadMaps().

registerAutoloadMap

Register a class map registerAutoloadMap($map)

registerAutoloadMap() Registers a class map with the autoloader. $map may be either a string referencing a PHP script that returns a class map, or an array defining a class map.

More than one class map may be registered; each will be merged with the previous, meaning it’s possible for a later class map to overwrite entries from a previously registered map.

registerAutoloadMaps

Register multiple class maps at once registerAutoloadMaps($maps)

registerAutoloadMaps() Register multiple class maps with the autoloader. Expects either an array or Traversable object; it then iterates over the argument and passes each value to registerAutoloadMap().

getAutoloadMap

Retrieve the current class map getAutoloadMap()

getAutoloadMap() Retrieves the state of the current class map; the return value is simply an array.

autoload

Attempt to load a class. autoload($class)

autoload() Attempts to load the class specified. Returns a boolean false on failure, or a string indicating the class loaded on success.

register

Register with spl_autoload. register()

register() Registers the autoload() method of the current instance with spl_autoload_register().

Examples

Using configuration to seed ClassMapAutoloader

Often, you will want to configure your ClassMapAutoloader. These values may come from a configuration file, a cache (such as ShMem or memcached), or a simple PHP array. The following is an example of a PHP array that could be used to configure the autoloader:

// Configuration defining both a file-based class map, and an array map
$config = array(
    APPLICATION_PATH . '/../library/autoloader_classmap.php', // file-based class map
    array(                              // array class map
        'Application\Bootstrap' => APPLICATION_PATH . '/Bootstrap.php',
        'Test\Bootstrap'        => APPLICATION_PATH . '/../tests/Bootstrap.php',
    ),
);

An equivalent INI style configuration might look like this:

classmap.library = APPLICATION_PATH "/../library/autoloader_classmap.php"
classmap.resources.Application\Bootstrap = APPLICATION_PATH "/Bootstrap.php"
classmap.resources.Test\Bootstrap = APPLICATION_PATH "/../tests/Bootstrap.php"

Once you have your configuration, you can pass it either to the constructor of the ClassMapAutoloader, to its setOptions() method, or to registerAutoloadMaps().

/* The following are all equivalent */

// To the constructor:
$loader = new Zend\Loader\ClassMapAutoloader($config);

// To setOptions():
$loader = new Zend\Loader\ClassMapAutoloader();
$loader->setOptions($config);

// To registerAutoloadMaps():
$loader = new Zend\Loader\ClassMapAutoloader();
$loader->registerAutoloadMaps($config);