Pengguna memasukkan nama pengguna dan kata laluan mereka untuk log masuk. Jika ia kosong, pangkalan data tidak dijumpai atau kata laluan salah, kembali dan log masuk semula. .

kod Seperti berikut:

<?php
/**
 * Created by PhpStorm.
 * User: Administrator
 * Date: 2018/2/27 0027
 * Time: 上午 10:47
 */
header('Content-type:text/html;charset=utf-8');
if ($_SERVER['REQUEST_METHOD'] == 'POST') {
    if (empty($_POST['username'])){
        echo "<script>alert('用戶名不能為空！');location.href='login.html';</script>";
    }else {
        $username=trim($_POST['username']);
    }
    if (empty($_POST['password'])){
        echo "<script>alert('密碼不能為空！');location.href='login.html';</script>";
    }else{
        $password=$_POST['password'];
    }
}
$mysqli = new mysqli('localhost', 'root', 'root', 'student');
$result = $mysqli->query("SELECT password FROM user WHERE username = "."'$username'");
$rs=$result->fetch_row();
if (!empty($rs)){
    if ($password != $rs[0]) {
        echo "<script>alert('密碼錯(cuò)誤！');location.href='login.html';</script>";
    }else{
        $expire=3600;
        ini_set('session.gc_maxlifetime', $expire);//保存1小時(shí)
        if (empty($_COOKIE['PHPSESSID'])) {
            session_set_cookie_params($expire);
            session_start();
        }else{
            session_start();
            setcookie('PHPSESSID', session_id(), time() + $expire);
        }
        if(isset($_SESSION['username'])){
            exit("您已經(jīng)登入了，請(qǐng)不要重新登入！用戶名：{$_SESSION['username']}---<a href='logout.php'>注銷</a>");
        }else{
            $_SESSION['username']=$_POST['username'];
        }
        echo "<script>alert('登錄成功！');</script><br>";
        echo "您好！{$_SESSION['username']},歡迎回來(lái)！";
        echo "<a href='logout.php'>注銷</a>";
    }
}else{
    echo "<script>alert('沒(méi)有此用戶！');location.href='login.html';</script>";
}