页面
<?php
//校验验证码
if (isset($_POST["authcode"])) {
session_start();
???if (strtolower($_POST["authcode"]) == $_SESSION["authcode"]) { ???????echo "<font color=‘#0000cc‘>输入正确</font>"; ???} else { ???????echo "<font color=‘#cc0000‘>输入错误</font>"; ???} ???exit();}?>
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8"/>
<title>确认验证码</title>
<script type="text/javascript"></script>
</head>
<body>
<form action="test.php" method="post">
<p>验证码图片：<img id="captcha_img" border="1" src="1.php?r=<?php echo rand();?>" width="100px" height="30"</p>
<a href="javascript:void(0)" onclick="document.getElementById(‘captcha_img‘).src=‘1.php?r=‘+Math.random()">换一个？</a>
<p>请输入图片中的内容：<input type="text" name="authcode" value="" /></p>
<p><input type="submit" value="提交" style="padding:6px 20px";></p>
</form>
</body>
</html>
后端php处理生成验证码
<?php
session_start();
header("content-type: image/png");
//生成白色底图$image = imagecreatetruecolor(100, 30);$bgcolor = imagecolorallocate($image, 255, 255, 255);imagefill($image, 0, 0, $bgcolor);//在白色底图上生成4个彩色随机字符/*1.生成4个数字for($i=0;$i<4;$i++) { ???$fontsize = 6; ???$fontcolor = imagecolorallocate($image, rand(0, 120), rand(0, 120), rand(0, 120)); ???$fontcontent = rand(0, 9); ???$x = ($i*100/4) + rand(5, 10); ???$y = rand(5, 10); ???imagestring($image, $fontsize, $x, $y, $fontcontent, $fontcolor);}*///2.生成随机字母数字$captch_code = "";//将生成的验证码存入该变量中for($i=0;$i<4;$i++) { ???$fontsize = 6; ???$fontcolor = imagecolorallocate($image, rand(0, 120), rand(0, 120), rand(0, 120)); ???//随机截取字母数字 ???$data = "abcdefghijkmnopqrstuvwxyz23456789"; ???$fontcontent = substr($data,rand(0,strlen($data)),1); ???$captch_code.= $fontcontent;//追加到验证码存放 ???$x = ($i*100/4) + rand(5, 10); ???$y = rand(5, 10); ???imagestring($image, $fontsize, $x, $y, $fontcontent, $fontcolor);}$_SESSION["authcode"] = $captch_code;//保存到session中//在白色底图上生成随机点(干扰元素)for($i=0;$i<200;$i++) { ???$pointcolor = imagecolorallocate($image, rand(50, 200), rand(50, 200), rand(50, 200)); ???imagesetpixel($image, rand(1, 29), rand(1, 29), $pointcolor);}//在白色底图上生成随机线(干扰元素)for($i=0;$i<3;$i++) { ???$linecolor = imagecolorallocate($image, rand(80, 220), rand(80, 220), rand(80, 220)); ???imageline($image, rand(1, 99), rand(1, 29), rand(1, 99), rand(1, 29), $linecolor);}imagepng($image);imagedestroy($image);?>``
PHP JS CSS session实现验证码功能
原文地址：http://blog.51cto.com/anfishr/2136878