ITEEDU

30.2. The Autoloader

Zend_Loader_Autoloader introduces a comprehensive autoloading solution for Zend Framework. It has been designed with several goals in mind:

  • Provide a true namespace autoloader. (Previous incarnations intercepted all userland namespaces.)

  • Allow registering arbitrary callbacks as autoloaders, and manage them as a stack. (At the time of this writing, this overcomes some issues with spl_autoload, which does not allow re-registering a callback that utilizes an instance method.)

  • Allow optimistic matching of namespaces to provide faster class resolution.

Zend_Loader_Autoloader implements a singleton, making it unversally accessible. This provides the ability to register additional autoloaders from anywhere in your code as necessary.

30.2.1. Using the Autoloader

The first time an instance of the autoloader is retrieved, it registers itself with spl_autoload. You retrieve an instance using the getInstance() method: 

$autoloader = Zend_Loader_Autoloader::getInstance();

By default, the autoloader is configured to match the "Zend_" and "ZendX_" namespaces. If you have your own library code that uses your own namespace, you may register it with the autoloader using the registerNamespace() method. For instance, if your library code is prefixed with "My_", you could do so as follows: 

$autoloader->registerNamespace('My_');
[注意] Namespace Prefixes

You'll note that the previous example uses "My_" and not "My". This is because Zend_Loader_Autoloader is intended as a general purpose autoloader, and does not make the assumption that a given class prefix namespace includes an underscore. If your class namespace does include one, you should include it when registering your namespace.

You can also register arbitrary autoloader callbacks, optionally with a specific namespace (or group of namespaces). Zend_Loader_Autoloader will attempt to match these first before using its internal autoloading mechanism.

As an example, you may want to utilize one or more eZcomponents components with your Zend Framework application. To use its autoloading capabilities, push it onto the autoloader stack using pushAutoloader(): 

$autoloader->pushAutoloader(array('ezcBase', 'autoload'), 'ezc');

This tells the autoloader to use the eZcomponents autoloader for classes beginning with "ezc".

You can use the unshiftAutoloader() method to add the autoloader to the beginning of the autoloader chain.

By default, Zend_Loader_Autoloader does no error suppression when using its internal autoloader, which utilizes Zend_Loader::loadClass(). Most of the time, this is exactly what you want. However, there may be cases where you want to suppress them. You can do this using suppressNotFoundWarnings(): 

$autoloader->suppressNotFoundWarnings(true);

Finally, there may be times when you want the autoloader to load any namespace. For instance, PEAR libraries do not share a common namespace, making specifying individual namespaces difficult when many PEAR components are in use. You can use the setFallbackAutoloader() method to have the autoloader act as a catch-all: 

$autoloader->setFallbackAutoloader(true);

30.2.2. The Autoloader Interface

Besides being able to specify arbitrary callbacks as autoloaders, Zend Framework also defines an interface autoloading classes may imlement, Zend_Loader_Autoloader_Interface: 

interface Zend_Loader_Autoloader_Interface
{
    public function autoload($class);
}

When using this interface, you can simply pass a class instance to Zend_Loader_Autoloader's pushAutoloader() and unshiftAutoloader() methods: 

// Assume Foo_Autoloader implements Zend_Loader_Autoloader_Interface:
$foo = new Foo_Autoloader();

$autoloader->pushAutoloader($foo, 'Foo_');

30.2.3. Autoloader Reference

Below, please find a guide to the methods available in Zend_Loader_Autoloader.

表 30.1. Zend_Loader_Autoloader Methods

Method Return Value Parameters Description
getInstance() Zend_Loader_Autoloader N/A

Retrieve the Zend_Loader_Autoloader singleton instance. On first retrieval, it registers itself with spl_autoload. This method is static.

resetInstance() void N/A

Resets the state of the Zend_Loader_Autoloader singleton instance to it's original state, unregistering all autoloader callbacks and all registered namespaces.

autoload($class) string|false

  • $class, required. A string class name to load.

Attempt to resolve a class name to a file and load it.

setDefaultAutoloader($callback) Zend_Loader_Autoloader

  • $callback, required.

Specify an alternate PHP callback to use for the default autoloader implementation.

getDefaultAutoloader() callback N/A

Retrieve the default autoloader implementation; by default, this is Zend_Loader::loadClass().

setAutoloaders(array $autoloaders) Zend_Loader_Autoloader

  • $autoloaders, required.

Set a list of concrete autoloaders to use in the autoloader stack. Each item in the autoloaders array must be a PHP callback.

getAutoloaders() Array N/A

Retrieve the internal autoloader stack.

getNamespaceAutoloaders($namespace) Array

  • $namespace, required

Fetch all autoloaders that have registered to load a specific namespace.

registerNamespace($namespace) Zend_Loader_Autoloader

  • $namespace, required.

Register one or more namespaces with the default autoloader. If $namespace is a string, it registers that namespace; if it's an array of strings, registers each as a namespace.

unregisterNamespace($namespace) Zend_Loader_Autoloader

  • $namespace, required.

Unregister one or more namespaces from the default autoloader. If $namespace is a string, it unregisters that namespace; if it's an array of strings, unregisters each as a namespace.

getRegisteredNamespace() Array N/A

Returns an array of all namespaces registered with the default autoloader.

suppressNotFoundWarnings($flag = null) boolean|Zend_Loader_Autoloader

  • $flag, optional.

Set or retrieve the value of the flag used to indicate whether the default autoloader implementation should suppress "file not found" warnings. If no arguments or a null value is passed, returns a boolean indicating the status of the flag; if a boolean is passed, the flag is set to that value and the autoloader instance is returned (to allow method chaining).

setFallbackAutoloader($flag) Zend_Loader_Autoloader

  • $flag, required.

Set the value of the flag used to indicate whether or not the default autoloader should be used as a fallback or catch-all autoloader for all namespaces.

isFallbackAutoloader() Boolean N/A

Retrieve the value of the flag used to indicate whether or not the default autoloader should be used as a fallback or catch-all autoloader for all namespaces. By default, this is false.

getClassAutoloaders($class) Array

  • $class, required.

Get the list of namespaced autoloaders that could potentially match the provided class. If none match, all global (non-namespaced) autoloaders are returned.

unshiftAutoloader($callback, $namespace = '') Zend_Loader_Autoloader

  • $callback, required. A valid PHP callback

  • $namespace, optional. A string representing a class prefix namespace.

Add a concrete autoloader implementation to the beginning of the internal autoloader stack. If a namespace is provided, that namespace will be used to match optimistically; otherwise, the autoloader will be considered a global autoloader.

pushAutoloader($callback, $namespace = '') Zend_Loader_Autoloader

  • $callback, required. A valid PHP callback

  • $namespace, optional. A string representing a class prefix namespace.

Add a concrete autoloader implementation to the end of the internal autoloader stack. If a namespace is provided, that namespace will be used to match optimistically; otherwise, the autoloader will be considered a global autoloader.

removeAutoloader($callback, $namespace = '') Zend_Loader_Autoloader

  • $callback, required. A valid PHP callback

  • $namespace, optional. A string representing a class prefix namespace, or an array of namespace strings.

Remove a concrete autoloader implementation from the internal autoloader stack. If a namespace or namespaces are provided, the callback will be removed from that namespace or namespaces only.