You need to introduce the database file config.php and the public file head.php
<?php include("head.php");?>
<?php include("config.php");?>The following is the complete login page code, the file name is landing.php.
<?php
include("config.php");
?>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>简单图书借阅系统登录</title>
<style>
body,td,th {font-family: 微软雅黑;font-size: 9px;color: #222;}
body {background-color: #FFFFFF;line-height:20px;}
a:link {color: #222;text-decoration: none;}
a:visited {text-decoration: none;color: #222;}
a:hover {text-decoration: underline;color: #FF0000;}
a:active {text-decoration: none;color: #999999;}
</style>
</head>
<?php
//初始化session
if(isset($_GET['tj']) == 'out'){
session_destroy();
echo "<script language=javascript>alert('退出成功！');window.location='landing.php'</script>";
}
if(isset($_POST['submit'])){
// 如果已经登录过，直接退出
if(isset($_SESSION['id'])) {
//重定向到管理留言
echo "<script language=javascript>alert('您已登陆');window.location='index.php'</script>";
// 登录过的话，立即结束
exit;
}
// 获得参数
$nickname=$_POST['username'];
$password=$_POST['password'];
//$password=md5($password);
// 检查帐号和密码是否正确,
$sql="select * from user where name='$nickname' and password='$password'";
$re = mysqli_query($link,$sql);
$result=mysqli_fetch_array($re);
// 如果用户登录正确
if(!empty($result)) {
//注册session变量，保存当前会话用户的昵称
$_SESSION['id']=$result['id'];
// 登录成功重定向到管理页面
echo "<script language=javascript>alert('登陆成功');window.location='index.php'</script>";
}
else {
// 管理员登录失败
echo "<script language=javascript>alert('密码不正确');window.location='landing.php'</script>";
}
}
?>
<body>
<?php include("head.php");?>
<form name="myform" method="post" onSubmit="return CheckPost()" action="" style="margin-bottom:5px;">
<table width="782" border="0" align="center" cellpadding="5" cellspacing="1" bgcolor="#CCCCCC">
<tr>
<td height="30" colspan="2" bgcolor="#FFFFFF">用户登录</td>
</tr>
<tr>
<td width="337" align="right" bgcolor="#FFFFFF">用户名:
</td>
<td width="422" bgcolor="#FFFFFF"><input type="text" name="username"></td>
</tr>
<tr>
<td align="right" bgcolor="#FFFFFF">密 码:
</td>
<td bgcolor="#FFFFFF"><input type="password" name="password"></td>
</tr>
<tr>
<td align="right" bgcolor="#FFFFFF"><a href="reg.php">注册新用户</a>
</td>
<td bgcolor="#FFFFFF"><input type="submit" name="submit" value="登录"></td>
</tr>
</table>
</form>
</body>
</html>
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