如何使用MySQL和PHP在每次登录时将用户的注销时间存储在数据库中？

Question

I'm new to PHP and MySQL. My project is about a school management system. In this project I have 3 users. Whenever they login, the login time is stored correctly each time. And when a user logs out , the log out time is stored. The problem is, the last logged out time is also updated to the previous log out times for that particular user. Thank You in advance

My code is:

login.php

$sql = $conn->query("Insert into userlog (username) values ('$username')");

Log out. php

<?php

include("php/dbconnect.php");
ob_start();


mysqli_query($conn,"UPDATE userlog SET logoutTime = NOW()  WHERE username = '$_SESSION[username]'   ");


unset($_SESSION['name']);

unset($_SESSION['uid']);

unset($_SESSION['username']);

echo '<script type="text/javascript">window.location="login.php"; </script>';


?>

I expect ,

id username login logout
1    1111   12:10  12:20
2    1111   12:40  12:50

But my output is like below,

id username login logout
1    1111   12:10  12:50
2    1111   12:40  12:50

Answer 1

You need to make sure you only update the latest login time, so add a condition to your WHERE clause to that effect:

mysqli_query($conn,"UPDATE userlog 
                    SET logoutTime = NOW()  
                    WHERE username = '$_SESSION[username]'
                      AND loginTime = (SELECT maxLoginTime 
                                       FROM (SELECT MAX(loginTime) AS maxLoginTime
                                             FROM userlog 
                                             WHERE username = '$_SESSION[username]') u)"
            );

Demo on dbfiddle