ZF Autoloader to load ancestor and requested class

Question

I am integrating Zend Framework into an existing application. I want to switch the application over to Zend's autoloading mechanism to replace dozens of include() statements.

I have a specific requirement for the autoloading mechanism, though. Allow me to elaborate.

The existing application uses a core library (independent from ZF), for example:

/Core/Library/authentication.php
/Core/Library/translation.php
/Core/Library/messages.php

this core library is to remain untouched at all times and serves a number of applications. The library contains classes like

class ancestor_authentication { ... }
class ancestor_translation { ... }
class ancestor_messages { ... }

in the application, there is also a Library directory:

/App/Library/authentication.php
/App/Library/translation.php
/App/Library/messages.php

these includes extend the ancestor classes and are the ones that actually get instantiated in the application.

class authentication extends ancestor_authentication { }
class translation extends ancestor_translation { }
class messages extends ancestor_messages { }

usually, these class definitions are empty. They simply extend their ancestors and provide the class name to instantiate.

$authentication = new authentication();

The purpose of this solution is to be able to easily customize aspects of the application without having to patch the core libraries.

Now, the autoloader I need would have to be aware of this structure. When an object of the class authentication is requested, the autoloader would have to:

1. load  /Core/Library/authentication.php
2. load  /App/Library/authentication.php

My current approach would be creating a custom function, and binding that to Zend_Loader_Autoloader for a specific namespace prefix.

• Is there already a way to do this in Zend that I am overlooking? The accepted answer in this question kind of implies there is, but that may be just a bad choice of wording.

• Are there extensions to the Zend Autoloader that do this?

• Can you - I am new to ZF - think of an elegant way, conforming with the spirit of the framework, of extending the Autoloader with this functionality? I'm not necessary looking for a ready-made implementation, some pointers (This should be an extension to the xyz method that you would call like this...) would already be enough.

Answer 1

See the manual on Zend_Loader:

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.

$autoloader->registerNamespace('My_');

Note that the autoloader follows the ZF Naming Convention, so Zend_Foo_Bar will look in Zend/Foo/Bar.php.

However,

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.

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

Another way would be to create custom class Loader extending Zend_Loader and then register it with:

Zend_Loader::registerAutoload('My_Loader');

ZF will then use this autoloader instead of the default one.

Answer 2

To extend what Gordon already pointed out, I'd create my own autoloader class that implements Zend_Loader_Autoloader_Interface and push that onto the Zend_Loader_Autoloader-stack.

class My_Autoloader implements Zend_Loader_Autoloader_Interface 
{
    public function autoload($class) 
    {
        // add your logic to find the required classes in here
    }
}

$autoloader = Zend_Loader_Autoloader::getInstance();
// pushAutoloader() or unshiftAutoloader() depending on where 
// you'd like to put your autoloader on the stack
// note that we leave the $namespace parameter empty
// as your classes don't share a common namespace
$autoloader->pushAutoloader(new My_Autoloader(), '');

I wouldn't go with the Zend_Loader approach as, even though not deprecated yet, the new Zend_Loader_Autoloader seems to be best practice currently.