//form.php
<?php
error_reporting(E_ALL & ~E_NOTICE);
//判断是否存在authorcode
if(isset($_REQUEST['authorcode'])){
session_start();
if(strtolower($_REQUEST['authorcode'])==$_SESSION['authorcode']){
echo '<script>alert("输入成功");</script>';
}else{
echo '<script>alert("输入错误");</script>';
}
}
?>
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>表单验证</title>
<script>
function change(){
//alert("sdd");
document.getElementById("captcha").src="captcha.php?/res="+Math.random();
}
</script>
</head>
<body>
<form action="form.php" method="post">
<h3>表单验证</h3>
<p>验证码图片：<img id="captcha" src="captcha.php?res=<?php echo rand();?>">
<a href="javascript:void(0)" onclick='change()'>换一个？</a>
</p>
<p>请输入验证码：<input type="text" name="authorcode" placeholder="请输入验证码中内容" value="">
</p>
<p><input type="submit" value="确定"></p>
</form>
</body>
</html>