Removing Drupal GET Form apparently unnecessary parameters
Here's a workaround you can use:

    $form['#after_build'][] = 'mymodule_form_modify';


Then:

    function mymodule_form_modify($form){
      unset($form['form_token']);
      unset($form['form_build_id']);
      unset($form['form_id']);
      return $form;
    }


And finally to get rid of the &amp;op parameter:

    $form['submit'] = array(
      '#type' =&gt; 'submit',
      '#value' =&gt; t('Submit'),
      '#name' =&gt; '',
    );


Source.