public function fetch ( $id ) {
        if (isset( self::$propData[$this->getKey( $id )] )) {
            return self::$propData[$this->getKey( $id )];
        }
        return false;
    }
public function fetch ( $id ) {
        if (isset( self::$propData[$this->getKey( $id )] )) {
            return self::$propData[$this->getKey( $id )];
        }
        return false;
    }
public function fetch ( $ id ) { if ( isset ( self :: $ propData [ $ this -> getKey ( $ id ) ] ) ) { return self :: $ propData [ $ this -> getKey ( $ id ) ] ; } return false ; }
fetch data if exists so the current object
is exchanges

@param mixed $id
@return self
fetch data if exists so the current object is exchanges