title: zend_form -- how to get form values except for disables elements
body: <p>i want to use zend_form to validate and filter the POST data,and some form fields are disabled element,
  but when i use $form->isValid($post) filtering the data and use $form->getValues() to  get the filtered data, it returns all the elements value (including the disabled elements value which i don't want). </p>
  
  <p>such as :</p>
  
  <pre><code>&lt;form method="post" action=""&gt;
  &lt;input type="text" disabled="disabled" name="account_id" value="123456"&gt;
  
  &lt;input type="text"  name="name" value=""&gt;
  &lt;input type="text"  name="email" value=""&gt;
  
  &lt;input type="text" disabled="disabled" name="created_date" value="2011-06-12"&gt;
  &lt;input type="text" disabled="disabled" name="created_by" value="admin"&gt;
  &lt;input type="submit"&gt;
  &lt;/form&gt;
  </code></pre>
  
  <p>so is there any way to get rid of the disables elements value ?
  (because there are many fields and disabled elements ,so i don't want to trim them manually)</p>
  
  <p>thanks!</p>