Here, I'am using this following function: Working in wordpress site.
    function wp_retrieve_information($latitude, $longitude){
    global $wpdb;
    $sql= "SELECT user_email, 
   ( 3959 * acos( cos( radians($latitude) ) * cos( radians( user_lat ) ) 
   * cos( radians(user_long) - radians($longitude)) + sin(radians($latitude)) 
   * sin( radians(user_lat)))) AS distance 
    FROM $wpdb->users 
    having distance < 10";
    $test= $wpdb->get_results($sql) or die(mysql_error());
    //print_r($test);
    foreach ($test as $row) {
    echo $row['user_email'];
    echo $row['distance'];
    }
    return true;
}
Here i'am using $latitude and $longitude as variable in sql query but when I try to call this function website is get totally blank.. may I know where i'am doing the mistake.
 
    