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; //默认搜索范围为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, "*");
        
        $i = 1;
        echo "纬度:$lat,经度:$lng, 周围".$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:".$v["uid"]." &nbsp;&nbsp;&nbsp; 纬度:".$v["lat"].",经度:".$v["lng"]." 距离:".$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);
    }