服务器Mac地址验证

Question

我正在创建一个应用程序，它通过我的服务器验证客户端的mac地址，状态，到期日期。我是php新手所以我创建了这个代码来获取POST请求以这种方式返回代码

status|Mac|EXP in milliseconds
102|2C59E54277E4|1516000210000

它应该在表上查找mac，然后获取以前一格式组合它们的值，并通过发布url回复上面的值

http://www.localhost.com/getLic.php?m=2C59E54277E4

<?php

// database connection parameters
$db_host = 'localhost';
$db_user = 'app';
$db_pass = '123456';
$db_name = 'app';

// client information table
$clients_tbl_name = 'clients';
$mac_tbl_col = "mac";

$mac = $_POST['m'];

function ServerResponse($mac = '', $lang_id = 1033)
{
    if($mac == '')
        return $msg_sep . "Missing Mac Address !";

    $db_conn = @mysql_connect($db_host, $db_user, $db_pass);
    if(!$db_conn)
        {
            echo " Connection error !";
        }
    // select target database
    $db_selected = @mysql_select_db($db_name, $db_conn);
    if(!$db_selected)
        {
        // issue error response
        echo " Database Not Found ! ";
        }
    $rero = mysql_query("SELECT CONCAT_WS('|', $status,$mac,$exp) FROM `". $clients_tbl_name ."` WHERE `". $mac ."` = '" . mysql_real_escape_string($serial) . "'");
    return mysql_result($rero);
}
echo ServerResponse($mac);
  die();
}

?>

代码有什么问题？它返回500内部服务器错误！