先看下示例效果：
目录结构：
> Captcha.class.php
> captcha.php
> demo.php
Captcha.class.php 验证码类
~~~
<?php
//验证码类
class Captcha {
private $charset = 'abcdefghkmnprstuvwxyzABCDEFGHKMNPRSTUVWXYZ23456789';//随机因子
private $code;//验证码
private $codelen = 4;//验证码长度
private $width = 130;//宽度
private $height = 50;//高度
private $img;//图形资源句柄
private $font;//指定的字体
private $fontsize = 20;//指定字体大小
private $fontcolor;//指定字体颜色
//构造方法初始化
public function __construct() {
$this->font = 'C:\Windows\Fonts\MATURASC.TTF';// 注意字体路径要写对，否则显示不了图片
}
//生成随机码
private function createCode() {
$_len = strlen($this->charset)-1;
for ($i=0;$i<$this->codelen;$i++) {
$this->code .= $this->charset[mt_rand(0,$_len)];
}
}
//生成背景
private function createBg() {
$this->img = imagecreatetruecolor($this->width, $this->height);
$color = imagecolorallocate($this->img, mt_rand(157,255), mt_rand(157,255), mt_rand(157,255));
imagefilledrectangle($this->img,0,$this->height,$this->width,0,$color);
}
//生成文字
private function createFont() {
$_x = $this->width / $this->codelen;
for ($i=0;$i<$this->codelen;$i++) {
$this->fontcolor = imagecolorallocate($this->img,mt_rand(0,156),mt_rand(0,156),mt_rand(0,156));
imagettftext($this->img,$this->fontsize,mt_rand(-30,30),$_x*$i+mt_rand(1,5),$this->height / 1.4,$this->fontcolor,$this->font,$this->code[$i]);
}
}
//生成线条、雪花
private function createLine() {
//线条
for ($i=0;$i<6;$i++) {
$color = imagecolorallocate($this->img,mt_rand(0,156),mt_rand(0,156),mt_rand(0,156));
imageline($this->img,mt_rand(0,$this->width),mt_rand(0,$this->height),mt_rand(0,$this->width),mt_rand(0,$this->height),$color);
}
//雪花
for ($i=0;$i<100;$i++) {
$color = imagecolorallocate($this->img,mt_rand(200,255),mt_rand(200,255),mt_rand(200,255));
imagestring($this->img,mt_rand(1,5),mt_rand(0,$this->width),mt_rand(0,$this->height),'*',$color);
}
}
//输出
private function outPut() {
header('Content-type:image/png');
imagepng($this->img);
imagedestroy($this->img);
}
//对外生成
public function doimg() {
$this->createBg();
$this->createCode();
$this->createLine();
$this->createFont();
$this->outPut();
}
//获取验证码
public function getCode() {
return strtolower($this->code);
}
}
~~~
captcha.php
~~~
<?php
session_start();
require 'Captcha.class.php'; //先把类包含进来，实际路径根据实际情况进行修改。
$_vc = new Captcha(); //实例化一个对象
$_vc->doimg();
$_SESSION['captcha'] = $_vc->getCode();//验证码保存到SESSION中
~~~
demo.php
~~~
<?php
session_start();
//在页首先要开启session,
//error_reporting(2047);
session_destroy();
//将session去掉，以每次都能取新的session值;
//用seesion 效果不错，也很方便
?>
<html>
<head>
<title>session 图片验证实例</title>
<style type="text/css">
#login p{ margin-top: 15px;line-height: 20px;font-size: 14px;font-weight: bold; }
form{margin-left:20px;}
</style>
</head>
<body>
<form id="login" action="" method="post">
<p>此例为session验证实例</p>
<p>
<span>验证码：</span>
<input type="text" name="validate" value="" size=10>
<img title="点击刷新" src="./captcha.php" align="absbottom" onclick="this.src=this.src"></img>
</p>
<p>
<input type="submit">
</p>
</form>
<?php
//打印上一个session;
//echo "上一个session：<b>".$_SESSION["captcha"]."</b><br>";
$validate="";
if(isset($_POST["validate"])){
$validate=$_POST["validate"];
echo "您刚才输入的是：".$_POST["validate"]."<br>状态：";
if($validate!=$_SESSION["captcha"]){
//判断session值与用户输入的验证码是否一致;
echo "<font color=red>输入有误</font>";
}else{
echo "<font color=green>通过验证</font>";
}
}
?>
~~~
参考链接：[[http://www.jb51.net/article/40341.htm](http://www.jb51.net/article/40341.htm)]
