/** 
     * 计算两个坐标之间的距离(米) 
     * @param float $fP1Lat 起点(纬度) 
     * @param float $fP1Lon 起点(经度) 
     * @param float $fP2Lat 终点(纬度) 
     * @param float $fP2Lon 终点(经度) 
     * @return int 
     */
    
   function distanceBetween($fP1Lat, $fP1Lon, $fP2Lat, $fP2Lon){  
        $fEARTH_RADIUS = 6378137;  
        //角度换算成弧度  
        $fRadLon1 = deg2rad($fP1Lon);  
        $fRadLon2 = deg2rad($fP2Lon);  
        $fRadLat1 = deg2rad($fP1Lat);  
        $fRadLat2 = deg2rad($fP2Lat);  
        //计算经纬度的差值  
        $fD1 = abs($fRadLat1 - $fRadLat2);  
        $fD2 = abs($fRadLon1 - $fRadLon2);  
        //距离计算  
        $fP = pow(sin($fD1/2), 2) +  
              cos($fRadLat1) * cos($fRadLat2) * pow(sin($fD2/2), 2);  
        return intval($fEARTH_RADIUS * 2 * asin(sqrt($fP)) + 0.5);  
    }