/**      * 获取指定日期所在月的开始日期与结束日期      * @param string $date      * @param boolean 为true返回开始日期，否则返回结束日期      * @return array      * @access private      */     private function getMonthRange( $date, $returnFirstDay = true ) {         $timestamp = strtotime( $date );         if ( $returnFirstDay ) {             $monthFirstDay = date( 'Y-m-1 00:00:00', $timestamp );             return $monthFirstDay;         } else {             $mdays = date( 't', $timestamp );             $monthLastDay = date( 'Y-m-' . $mdays . ' 23:59:59', $timestamp );             return $monthLastDay;         }     }