在PHP中不允许多个登录

Question

我有一个用户登录的系统。每次特定用户登录时，我都会使用TIMESTAMP:将登录日期时间存储在MySQL数据库中

数据库中的每条记录都有一个user_id和login_date，并存储在我的att_log表中。但是，我想确保用户每天只能根据日期登录一次。这是我迄今为止的代码

        <?php
        include('conn.php');
        if (isset($_POST['submit'])) {
        $UserName=$_POST['id_emp']; 
        $Password=$_POST['password'];
        $result=mysql_query("select * from employee where id_emp='$UserName' and password='$Password'" )or die (mysql_error()); 
        $count=mysql_num_rows($result);
        $row=mysql_fetch_array($result);
        if ($count > 0){
        $_SESSION['emp_id']=$row['emp_id'];
        mysql_query("insert into att_log (username,login_date,id)values('$UserName',NOW(),".$row['emp_id'].")")or die(mysql_error());
?>

我该如何写一个正确的语句来检查情况——如果user_id在相同的日期登录，它会在插入att_log表之前拒绝。使用当前代码，它将在同一日期一次又一次地连续插入同一用户，只是时间不同。

我想在特定的日子过滤掉特定的用户，因为我会在月底计算他们的频率，就像一样

id_attlog  username   logindate           id   
1           2010    2015-06-20 19:08:19   33
2           2011    2015-06-20 19:08:19   34
3           2011    2015-06-21 19:08:19   34
4           2011    2015-06-22 19:08:19   34

User ID   Day of Attendance
33          3
34          1

其中用户id 34已经登录了3天并且用户33只登录了1天。因此，我希望用户每天只能登录一次。我仍在寻找正确的方式来实现对用户的限制，让他们每天登录一次。

谢谢！

Answer 1

// Compare username/password and check last login date is less than today
$result = mysql_query('select a.*, max(b.login_date) as login_date from employee AS a LEFT JOIN att_log AS b ON a.emp_id = b.id where a.emp_id = "' . mysql_real_escape_string($UserName) . '" and a.password = "' . mysql_real_escape_string($Password) . '" and login_date < DATE(NOW()) GROUP BY a.emp_id' ) or die (mysql_error());
if (mysql_num_rows($result) > 0) {
    $row = mysql_fetch_array($result);
    mysql_query('insert into att_log (username, login_date, id) values("' . mysql_real_escape_string($UserName) . '", NOW(), "' . mysql_real_escape_string($row['emp_id']) . '"') or die(mysql_error());
} else {
    echo 'Access denied';
}

或：

// Compare username/password
$result = mysql_query('select a.*, max(b.login_date) as login_date from employee AS a INNER JOIN att_log AS b ON a.emp_id = b.id where a.emp_id = "' . mysql_real_escape_string($UserName) . '" and a.password = "' . mysql_real_escape_string($Password) . '" GROUP BY a.emp_id' ) or die (mysql_error());
$row = mysql_fetch_array($result);
// If last login date is greater or equal than the start of today, show access denied message
if (strtotime($row['login_date']) >= strtotime(date('Y-m-d 00:00:00')) {
    echo 'Sorry you have already logged in today';
} else {
    mysql_query('insert into att_log (username, login_date, id) values("' . mysql_real_escape_string($UserName) . '", NOW(), "' . mysql_real_escape_string($row['emp_id']) . '"') or die(mysql_error());
}