$params = array('submit' => 'post', 'preview' => 'preview', 'delete' => 'delete', 'poll_delete' =>
'poll_delete', 'poll_add' => 'add_poll_option', 'poll_edit' => 'edit_poll_option', 'mode' => 'mode');
foreach($_REQUEST as $key => $value)
  if( array_has_key($params, $key) )
    ${$params[$key]} = $value;