To treat a group of objects the same way as a single instance of the object.

• a form class instance handles all its form elements like a single instance of the form, when render() is called, it subsequently runs through all its child elements and calls render() on them
• Zend_Config: a tree of configuration options, each one is a Zend_Config object itself

You can also find these code on GitHub

RenderableInterface.php

.. literalinclude:: RenderableInterface.php
   :language: php
   :linenos:

Form.php

.. literalinclude:: Form.php
   :language: php
   :linenos:

InputElement.php

.. literalinclude:: InputElement.php
   :language: php
   :linenos:

TextElement.php

.. literalinclude:: TextElement.php
   :language: php
   :linenos:

Tests/CompositeTest.php

.. literalinclude:: Tests/CompositeTest.php
   :language: php
   :linenos: