original_string: public function add_validation_rule(callable $callback) {
          if ($this->mode == self::MODE_COMPLETE) {
              $this->_form->addFormRule($callback);
          }
      }
code: public function add_validation_rule(callable $callback) {
          if ($this->mode == self::MODE_COMPLETE) {
              $this->_form->addFormRule($callback);
          }
      }
code_tokens: public function add_validation_rule ( callable $ callback ) { if ( $ this -> mode == self :: MODE_COMPLETE ) { $ this -> _form -> addFormRule ( $ callback ) ; } }
docstring: Adds a validation rule to the form
  
  @param callable $callback with arguments ($values, $files)
docstring_tokens: Adds a validation rule to the form