实例一登录

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>无标题文档</title>
</head>

<body>
<h1>登录</h1>
<form action="dlchuli.php" method="post">
<div>用户名：<input type="text" name="uid" /></div>
<div>密码：<input type="text" name="pwd" /></div>
<input type="submit" value="登录" />
</form>
</body>
</html>

登录处理验证

<?php
$uid = $_POST["uid"];
$pwd = $_POST["pwd"];

//造对象
$db = new MySQLi("localhost","root","123","mydb");
//判断是否出错
!mysqli_connect_error() or die("连接失败！");
//写SQL语句
//容易被SQL注入攻击,不安全
//$sql = "select count(*) from Users where Uid = '{$uid}' and Pwd='{$pwd}'";


$sql = "select Pwd from Users where Uid='{$uid}'";

//执行SQL语句
$result = $db->query($sql);

//取数据
$attr = $result->fetch_row();

if($attr[0] == $pwd)
{
	header("location:main.php");
}
else
{
	echo "登录失败！";
}