用户登录后的session操作（过期时间的设置）
用户输入用户名密码进行登录。如果为空，数据库未找到或者密码错误则返回重新登录。
登录成功后显示：
设置了session的过期时间然后跳转到：
如果用户已经登录则跳转到：
代码如下：
success.php
<?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('用户名不能为空！');location.href='login.html';</script>";
}else {
$username=trim($_POST['username']);
}
if (empty($_POST['password'])){
echo "<script>alert('密码不能为空！');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('密码错误！');location.href='login.html';</script>";
}else{
$expire=3600;
ini_set('session.gc_maxlifetime', $expire);//保存1小时
if (empty($_COOKIE['PHPSESSID'])) {
session_set_cookie_params($expire);
session_start();
}else{
session_start();
setcookie('PHPSESSID', session_id(), time() + $expire);
}
if(isset($_SESSION['username'])){
exit("您已经登入了，请不要重新登入！用户名：{$_SESSION['username']}---<a href='logout.php'>注销</a>");
}else{
$_SESSION['username']=$_POST['username'];
}
echo "<script>alert('登录成功！');</script><br>";
echo "您好！{$_SESSION['username']},欢迎回来！";
echo "<a href='logout.php'>注销</a>";
}
}else{
echo "<script>alert('没有此用户！');location.href='login.html';</script>";
}
