public function performValidation(ZFormElement $target)
 {
     if ($this->_validator && ($this->_runat & self::SERVER) != 0) {
         $validator = new ZValidator();
         if ($this->_options) {
             $args = array_pad($this->_options, count($this->_options) * -1 - 1, $target->getValue());
             return call_user_func_array(array($validator, $this->_validator), $args);
         } else {
             return $validator->{$this->_validator}($target->getValue());
         }
     }
     return false;
 }