php mysql 搜索附近的人

function get_member_action(){         $lat  = $_GET["lat"];         $lng  = $_GET["lng"];         $dist = $_GET["dist"];         //$lat  = "22.64609400";         //$lng  = "114.11702000";         //$dist = 1000;         //$sql = "select * from hzg_member where ((lat-22.64609400)*(lat-22.64609400)+(lng-114.11702000)*(lng-114.11702000)) < 0.0081 order by ((lat-22.64609400)*(lat-22.64609400)+(lng-114.11702000)*(lng-114.11702000)) asc";                  $arc   = $dist / 1000 * 0.009; //默認搜索範圍爲1000米 0.009度         $where = " ((lat-$lat)*(lat-$lat)+(lng-$lng)*(lng-$lng)) < $arc*$arc order by ((lat-$lat)*(lat-$lat)+(lng-$lng)*(lng-$lng)) asc";         $rows  = $this->obj->DB_select_all("member", $where, "*");                  $i = 1;         echo "緯度:$lat,經度:$lng, 周圍".$dist."米的人共有: ".count($rows)." 人<br/>";         foreach($rows as $key => $v){             $dist = $this->getDistance($lat,$lng,$v["lat"],$v["lng"]);             echo $i++." ".$v["username"]." uid:".$v["uid"]." &nbsp;&nbsp;&nbsp; 緯度:".$v["lat"].",經度:".$v["lng"]." 距離:".$dist." 米<br/>";         }     }          function getDistance($lat1, $lng1, $lat2, $lng2)     {         $earthRadius = 6367000; //approximate radius of earth in meters           $lat1 = ($lat1 * pi() ) / 180;         $lng1 = ($lng1 * pi() ) / 180;           $lat2 = ($lat2 * pi() ) / 180;         $lng2 = ($lng2 * pi() ) / 180;           $calcLongitude = $lng2 - $lng1;         $calcLatitude = $lat2 - $lat1;         $stepOne = pow(sin($calcLatitude / 2), 2) + cos($lat1) * cos($lat2) * pow(sin($calcLongitude / 2), 2);         $stepTwo = 2 * asin(min(1, sqrt($stepOne)));         $calculatedDistance = $earthRadius * $stepTwo;                  return round($calculatedDistance);     }