public function isValid(\form\Field $field)
 {
     if (!is_null($field->get_param('value'))) {
         return in_array($field->get_param('value'), $this->_array);
     }
     return false;
 }
 public function isValid(\form\Field $field)
 {
     if (!is_null($field->get_param('value'))) {
         return preg_match($this->_regex, $field->get_param('value'));
     }
     return false;
 }
 public function isValid(\form\Field $field)
 {
     if (!is_null($field->get_param('value'))) {
         if ($this->_required && empty($field->get_param('value')) || is_numeric($field->get_param('value')) === false) {
             return false;
         }
         $value = (int) $field->get_param('value');
         if ($value > $this->_max) {
             return false;
         }
         if ($value < $this->_min) {
             return false;
         }
         return true;
     }
     return false;
 }