A number of Zend Framework components are pluggable, and allow loading of dynamic functionality by specifying a class prefix and path to class files that are not necessarily on the include_path or do not necessarily follow traditional naming conventions. Zend_Loader_PluginLoader provides common functionality for this process.

The basic usage of the PluginLoader follows Zend Framework naming conventions of one class per file, using the underscore as a directory separator when resolving paths. It allows passing an optional class prefix to prepend when determining if a particular plugin class is loaded. Additionally, paths are searched in LIFO order. Due to the LIFO search and the class prefixes, this allows you to define namespaces for your plugins, and thus override plugins from paths registered earlier.