PHP MYSQL 搜索周边坐标，并计算两个点之间的距离

/**
 * 获取周围坐标
 * Enter description here ...
 * @param unknown_type $lng  固定坐标经度
 * @param unknown_type $lat  固定坐标纬度
 * @param unknown_type $distance  搜索周边距离，单位KM
 * @return multitype:multitype:number
 */
function returnSquarePoint($lng, $lat,$distance = 1){
    $earthRadius = 6378.138; //地球半径，单位KM
    $dlng =  2 * asin(sin($distance / (2 * $earthRadius)) / cos(deg2rad($lat)));
    $dlng = rad2deg($dlng);
    $dlat = $distance/$earthRadius;
    $dlat = rad2deg($dlat);
    return array(
        ‘left-top‘=>array(‘lat‘=>$lat + $dlat,‘lng‘=>$lng-$dlng),
        ‘right-top‘=>array(‘lat‘=>$lat + $dlat, ‘lng‘=>$lng + $dlng),
        ‘left-bottom‘=>array(‘lat‘=>$lat - $dlat, ‘lng‘=>$lng - $dlng),
        ‘right-bottom‘=>array(‘lat‘=>$lat - $dlat, ‘lng‘=>$lng + $dlng)
    );
    
    //使用此函数计算得到结果后，带入sql查询。
//    $squares = returnSquarePoint($lng, $lat);
//    $info_sql = "select id,locateinfo,lat,lng from `lbs_info` where lat<>0 and lat>{$squares[‘right-bottom‘][‘lat‘]} and lat<{$squares[‘left-top‘][‘lat‘]} and lng>{$squares[‘left-top‘][‘lng‘]} and lng<{$squares[‘right-bottom‘][‘lng‘]} "; 
}

/**
 * 计算两个坐标的直线距离 
 * Enter description here ...
 * @param unknown_type $lat1  
 * @param unknown_type $lng1
 * @param unknown_type $lat2
 * @param unknown_type $lng2
 */
function getDistance($lat1, $lng1, $lat2, $lng2){      
    $earthRadius = 6378.138; //近似地球半径千米
    // 转换为弧度
    $lat1 = ($lat1 * pi()) / 180;
    $lng1 = ($lng1 * pi()) / 180;
    $lat2 = ($lat2 * pi()) / 180;
    $lng2 = ($lng2 * pi()) / 180;
    // 使用半正矢公式  用尺规来计算
    $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);
}