本文实例讲述了PHP实现简单实用的验证码类。分享给大家供大家参考。具体如下：

<?php

/**

* @version 1.0

* @author bolted snail

* @date 2011-10-15

* @PHP验证码类

* 使用方法：

* $image=new Captcha();

* $image->config('宽度','高度','字符个数','验证码session索引');

* $image->create();//这样就会向浏览器输出一张图片

* //所有参数都可以省略，

* 默认是：宽80 高20 字符数4 验证码session索引captcha_code

* 第四个参数即把验证码存到$_SESSION['captcha_code']

* 最简单使用示例:

* $image=new Captcha();

* $image->create();//这样就会向浏览器输出一张图片

*/

class Captcha

{

private $width=80,$height=20,$codenum=4;

public $checkcode; //产生的验证码

private $checkimage; //验证码图片

private $disturbColor = ''; //干扰像素

private $session_flag='captcha_code';//存到session中的索引

//尝试开始session

function __construct(){

@session_start();

}

/*

* 参数：（宽度，高度，字符个数）

*/

function config($width='80',$height='20',$codenum='4',$session_flag='captcha_code')

{

$this->width=$width;

$this->height=$height;

$this->codenum=$codenum;

$this->session_flag=$session_flag;

}

function create()

{

//输出头

$this->outFileHeader();

//产生验证码

$this->createCode();

//产生图片

$this->createImage();

//设置干扰像素

$this->setDisturbColor();

//往图片上写验证码

$this->writeCheckCodeToImage();

imagepng($this->checkimage);

imagedestroy($this->checkimage);

$_SESSION[$this->session_flag]=$this->checkcode;

}

/*

* @brief 输出头

*/

private function outFileHeader()

{

header ("Content-type: image/png");

}

/**

* 产生验证码

*/

private function createCode()

{

$this->checkcode = strtoupper(substr(md5(rand()),0,$this->codenum));

}

/**

* 产生验证码图片

*/

private function createImage()

{

$this->checkimage = @imagecreate($this->width,$this->height);

$back = imagecolorallocate($this->checkimage,255,255,255);

$border = imagecolorallocate($this->checkimage,0,0,0);

imagefilledrectangle($this->checkimage,0,0,$this->width - 1,$this->height - 1,$back); // 白色底

imagerectangle($this->checkimage,0,0,$this->width - 1,$this->height - 1,$border); // 黑色边框

}

/**

* 设置图片的干扰像素

*/

private function setDisturbColor()

{

for ($i=0;$i<=200;$i++)

{

$this->disturbColor = imagecolorallocate($this->checkimage, rand(0,255), rand(0,255), rand(0,255));

imagesetpixel($this->checkimage,rand(2,128),rand(2,38),$this->disturbColor);

}

}

/**

*

* 在验证码图片上逐个画上验证码

*

*/

private function writeCheckCodeToImage()

{

for ($i=0;$i<$this->codenum;$i++)

{

$bg_color = imagecolorallocate ($this->checkimage, rand(0,255), rand(0,128), rand(0,255));

$x = floor($this->width/$this->codenum)*$i;

$y = rand(0,$this->height-15);

imagechar ($this->checkimage, rand(5,8), $x+5, $y, $this->checkcode[$i], $bg_color);

}

}

function __destruct()

{

unset($this->width,$this->height,$this->codenum,$this->session_flag);

}

}

?>

希望本文所述对大家的php程序设计有所帮助。