Zend_Http_Client is based on a connection adapter design. The connection adapter is the object in charge of performing the actual connection to the server, as well as writing requests and reading responses. This connection adapter can be replaced, and you can create and extend the default connection adapters to suite your special needs, without the need to extend or replace the entire HTTP client class, and with the same interface.

Currently, the Zend_Http_Client class provides four built-in connection adapters:

The Zend_Http_Client object's adapter connection adapter is set using the 'adapter' configuration option. When instantiating the client object, you can set the 'adapter' configuration option to a string containing the adapter's name (eg. 'Zend_Http_Client_Adapter_Socket') or to a variable holding an adapter object (eg. new Zend_Http_Client_Adapter_Test). You can also set the adapter later, using the Zend_Http_Client->setConfig() method.