这个利用PHP动态随机生成验证码的类是在LAMP的书上看到的。感觉写的很好就收藏了下来。

下面是效果图，这个效果图是没有开启干扰码的效果图

下面是类代码

 
<?php 
/************************************************ 
//FILE:ImageCode 
//DONE:生成动态验证码类 
//DATE"2010-3-31 
//Author:www.5dkx.com 5D开心博客 
************************************************************************/ 
class ImageCode{ 
private $width; //验证码图片宽度 
private $height; //验证码图片高度 
private $codeNum; //验证码字符个数 
private $checkCode; //验证码字符 
private $image; //验证码画布 
/************************************************************************ 
// Function:构造函数 
// Done:成员属性初始化 
// Author:www.5dkx.com 5D开心博客 
************************************************************************/ 
function __construct($width=60,$height=20,$codeNum=4) 
{ 
$this->width = $width; 
$this->height = $height; 
$this->codeNum = $codeNum; 
$this->checkCode = $this->createCheckCode(); 
} 
function showImage() 
{ 
$this->getcreateImage(); 
$this->outputText(); 
$this->setDisturbColor(); 
$this->outputImage(); 
} 
function getCheckCode() 
{ 
return $this->chekCode; 
} 
private function getCreateImage() 
{ 
$this->image = imagecreatetruecolor($this->width,$this->height); 
$back = imagecolorallocate($this->image,255,255,255); 
$border = imagecolorallocate($this->image,255,255,255); 
imagefilledrectangle($this->image,0,0,$this->width-1,$this->height-1,$border); 
//使用纯白色填充矩形框，这里用的话后面干扰码失效 
/*如果想用干扰码的话使用下面的*/ 
//imagerectangle($this->image,0,0,$this->width-1,$this->height-1,$border); 
} 
private function createCheckCode() 
{ 
for($i=0;$i<$this->codeNum;$i++) 
{ 
$number = rand(0,2); 
switch($number) 
{ 
case 0: $rand_number = rand(48,57); break;//数字 
case 1: $rand_number = rand(65,90);break;//大写字母 
case 2: $rand_number = rand(97,122);break;//小写字母 
} 
$asc = sprintf("%c",$rand_number); 
$asc_number = $asc_number.$asc; 
} 
return $asc_number; 
} 
private function setDisturbColor()//干扰吗设置 
{ 
for($i=0;$i<=100;$i++) 
{ 
//$color = imagecolorallocate($this->image,rand(0,255),rand(0,255),rand(0,255)); 
$color = imagecolorallocate($this->image,255,255,255); 
imagesetpixel($this->image,rand(1,$this->width-2),rand(1,$this->height-2),$color); 
} 
//$color = imagecolorallocate($this->image,0,0,0); 
//imagesetpixel($this->image,rand(1,$this->width-2),rand(1,$this->height-2),$color); 
} 
private function outputText() 
{ 
//随机颜色、随机摆放、随机字符串向图像输出 
for($i=0;$i<=$this->codeNum;$i++) 
{ 
$bg_color = imagecolorallocate($this->image,rand(0,255),rand(0,128),rand(0,255)); 
$x = floor($this->width/$this->codeNum)*$i+3; 
$y = rand(0,$this->height-15); 
imagechar($this->image,5,$x,$y,$this->checkCode[$i],$bg_color); 
} 
} 
private function outputImage() 
{ 
if(imagetypes()&IMG_GIF) 
{ 
header("Content_type:image/gif"); 
imagegif($this->image); 
} 
elseif(imagetypes()&IMG_JPG) 
{ 
header("Content-type:image/jpeg"); 
imagejpeg($this->image,"",0.5); 
} 
elseif(imagetypes()&IMG_PNG) 
{ 
header("Content-type:image/png"); 
imagejpeg($this->image); 
} 
elseif(imagetypes()&IMG_WBMP) 
{ 
header("Content-type:image/vnd.wap.wbmp"); 
imagejpeg($this->image); 
} 
else 
{ 
die("PHP不支持图像创建"); 
} 
} 
function __destruct() 
{ 
imagedestroy($this->image); 
} 
} 
/*显示*/ 
/******************************************************************* 
session_start(); 
$image = new ImageCode(60,20,4); 
$image->showImage(); 
$_SESSION['ImageCode'] = $image->getCheckCode(); 
*******************************************************************/ 
?>