PHP+Ajax implements verification code to verify user login
This article mainly introduces the relevant information of PHP AJAX verification code to verify user login in detail. Interested friends can refer to it. I hope it will be helpful to everyone.
One advantage of using AJAX to verify user login is that the jump page does not need to be refreshed. In addition, it is safer to use the verification code, so I wrote it down after a while. A total of three files are used:
yz.php: The PHP file that generates the verification code. The verification code will be in the SESSION for comparison and call during login
index.php: HTML file for user login
loginCheck.php: File for verifying user login
The following is analyzed one by one:
yz.php file
<?php
session_start();
//生成验证码图
Header("Content-type: image/PNG");
//长与宽
$im = imagecreate(44,18);
// 设置背景色:
$back = ImageColorAllocate($im, 245,245,245);
// 填充背景色:
imagefill($im,0,0,$back);
srand((double)microtime()*1000000);
$vcodes;
//生成4位数字
for($i=0;$i<4;$i++){
$font = ImageColorAllocate($im, rand(100,255),rand(0,100),rand(100,255));
$authnum=rand(1,9);
$vcodes.=$authnum;
imagestring($im, 5, 2+$i*10, 1, $authnum, $font);
}
//加入干扰象素
for($i=0;$i<100;$i++){
$randcolor = ImageColorallocate($im,rand(0,255),rand(0,255),rand(0,255));
imagesetpixel($im, rand()%70 , rand()%30 , $randcolor);
}
ImagePNG($im);
ImageDestroy($im);
// 将四位的验证码保存在 SESSION 里，登录时调用对比
$_SESSION["VCODE"]=$vcodes;
?>##index .php: Note, do not take $_SESSION["VCODE"] in this file, otherwise it will be taken one step later, and the previous verification code can be displayed only after refreshing.
Verify in loginCheck.php Okay<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html;charset=gb2312">
<title>管理后台| 请登录</title>
<link rel="stylesheet" type="text/css" href="\css\a.css">
<style type="text/css">
<!--
#main{
font-family:宋体;
font-size:10pt;
text-align:center;
margin-top:510px;
}
body{
background-attachment:fixed;
background-position:center;
background-image:url(./images/w2.jpg);
background-repeat: no-repeat;
}
#authCode{background-Color:#F8F9FF;}
table{text-align:center;}
//-->
</style>
<script type="text/javascript" src="./js/trim.js"></script>
<script type="text/javascript">
<!--
function clearX(){
document.getElementById('authCode').value="";
}
// 点击图片重新获得新的验证码：
function getVCode() {
var vcode=document.getElementById('vcode');
vcode.src ='yz.php?nocache='+new Date().getTime();
}
//定义XMLHttpRequest对象
var xmlHttp;
// 创建 XMLHttpRequest:
function createXmlHttpRequest(){
var xmlHttp=null;
try{
// Firefox, Opera 8.0+, Safari
xmlHttp=new XMLHttpRequest();
}catch(e){
// Internet Explorer
try{
xmlHttp=new ActiveXObject("Msxml2.XMLHTTP");
}catch(e){
xmlHttp=new ActiveXObject("Microsoft.XMLHTTP");
}
}
return xmlHttp;
}
// AJAX 检查登录: 有密码，要用POST 提交
function login(){
var authCode=trim(document.getElementById('authCode').value);
var username=trim(document.getElementById('username').value);
var password=trim(document.getElementById('password').value);
if(username=="" || password=="" || authCode==""){
alert("请输入用户名和密码和验证码！");
return false;
}else{
if(!xmlHttp) xmlHttp=createXmlHttpRequest();
var send_string="username="+username+"&password="+password+"&authCode="+authCode+"&fresh="+Math.random();
xmlHttp.open("POST","loginCheck.php",true);
xmlHttp.setRequestHeader("Content-Type","application/x-www-form-urlencoded");
xmlHttp.send(send_string);
xmlHttp.onreadystatechange=function(){
if(xmlHttp.readystate==4 && xmlHttp.status==200){
var answer=xmlHttp.responseText;
if(answer=="ok") //跳转到管理中心页面
window.location.href="adminCenter.php";
else{
alert("用户名密码或验证码不正确! 请重新输入!");
document.getElementById('username').focus();
}
}
}
}
}
//-->
</script>
</head>
<body onload="document.getElementById('username').focus();">
<p id="main">
<table>
<tr>
<td>用户名:<input type="text" id="username" /></td>
<td>密 码:<input type="password" id="password" /></td>
<td>验证码:<input type="text" id="authCode" size="6" maxlength="4" value="验证码" onfocus="clearX()"/></td>
<td><img id="vcode" src="yz.php" alt="看不清？点击换一张" onclick="getVCode()" /></td>
<td><input id="loginButton" type="submit" value="登 录" onclick="login()"/></td>
</tr>
</table>
</p>
</body>
</html>loginCheck.php File to verify user login
<?php
session_start();
include("../conn/connDB.php");
// 取得POST过来的参数:
$username=$_POST["username"];
$password=md5($_POST["password"]);
$authCode=$_POST["authCode"];
$feedback="no";
//对比是否==SESSION中的验证码，不能放在客户端做，否则取不正确的值
if($authCode==$_SESSION["VCODE"]){
$SQL="select * from users where username='$username' and password='$password'";
$result=mysql_query($SQL);
$rows=mysql_num_rows($result);
if($rows==1) // 验证成功
$feedback="ok";
$_SESSION["admin"]=true; //为了后台安全，存入SESSION，表明 ADMIN 已登录，供后面调用
}
echo $feedback;
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