PHP学习-验证用户名密码

登录页：login.php

 <?php
 //登录
 if(!isset($_POST['submit'])){exit('非法访问!');}
 $username = $_POST['adname'];
 $password = $_POST['adpass'];
 //包含数据库连接文件
 include('conn.php');
 //检测用户名及密码是否正确
 $check_query = mysql_query("select * from admin where ad_name='$username' and ad_code='$password' limit 1");
 if($result = mysql_fetch_array($check_query)){
     //登录成功
     session_start();
     $_SESSION['username'] = $username;
     $_SESSION['userid'] = $result['ad_id'];
     echo $username,' 欢迎你！进入 <a href="my.php">用户中心</a><br />';
     echo '点击此处 <a href="login.html">注销</a> 登录！<br />';
     exit;
 } else {
     exit('登录失败！点击此处 <a href="javascript:history.back(-1);">返回</a> 重试');
 }
 //注销登录
 if($_GET['action'] == "logout"){
     unset($_SESSION['userid']);
     unset($_SESSION['username']);
     echo '注销登录成功！点击此处 <a href="login.html">登录</a>';
     exit;
 }
 ?>

$_POST["a"]：获取post提交的数据a的值

mysql_query("select * from admin where ad_name='$username' and ad_code='$password' limit 1");执行一条MySQL查询

mysql_fetch_array($check_query)：获取根据如上数据表查询的一行信息