public function is_set($field) {
        return (isset($this->data[$field]) || isset($this->extradata[$field]));
    }
public function is_set($field) {
        return (isset($this->data[$field]) || isset($this->extradata[$field]));
    }
public function is_set ( $ field ) { return ( isset ( $ this -> data [ $ field ] ) || isset ( $ this -> extradata [ $ field ] ) ) ; }
Checks if a field is set.

@param string $field
@return bool
Checks if a field is set .