mysql-PHP+MYSQL，登出時，儲存最後登陸的IP及時間，代碼為何未生效？

mysqlphp

//-----------登出begin------------------------------------------if ( $_GET['action'] == "logout" ){    //登出前，記錄最後一次成功登陸的IP及日期    include('conn.php');    $client_ip = $_SERVER["HTTP_CLIENTIP"];    $user_id = $_SESSION['user_id'];    echo $client_ip;    echo $user_id;    sleep(10);    mysql_query("update users SET user_last_log_ip = $client_ip,user_last_log_date = unix_timestamp(now()) where user_id = $user_id limit 1");    mysql_close($con);     //刪除SESSION    unset($_SESSION['user_id']);    unset($_SESSION['user_email']);     unset($_SESSION['user_nickname']);     echo '
'.'登出成功！';    exit;}

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