title: PHP - $request->getPost('first_name')
body: <pre><code>public function process(Zend_Controller_Request_Abstract $request)
  {
       $this-&gt;first_name = $this-&gt;sanitize($request-&gt;getPost('first_name'));
  ....
  }
  </code></pre>
  
  <p>My question is <code>$request</code> is an instance of class <code>zend_controller_request_abstract</code>, but getpost is a function defined in class <code>zend_controller_request_http</code> which extends <code>zend_controller_request_abstract</code>, so why does <code>$request</code> invoke <code>getPost()</code> directly?</p>