我的php验证码类

<?php
/*
 * Created on 2010-3-11
 * author:zhangfei
 *我的验证码类
 */
 session_start();
 class Check_Class{
  public $h_img ;
public $c_back ;
public $c_front ;
//构造函数
function Check_Class(){
$h_img  =  imagecreate(100,30);
$c_back  =  imagecolorallocate($h_img,0,0,0);
$c_front  =  imagecolorallocate($h_img,255,255,255);
$_SESSION[randstr]=$randm_string = $this->random(5);//用session保存起来用以后面判断
$this->getLine($h_img);
$this->getPoint($h_img);
$this->paintString($h_img,$randm_string,$c_front);
//显示图片
header("Content-type:  image/jpeg");
imagejpeg($h_img);
imagedestroy($h_img);
}
  //产生随机字符串，包括数字和大小写字母
  function random($length)
{
   $hash = "";
   $chars = "CEFGHIJKLMNOPQRSTUVWXYZ0123456789cefghijklmnopqrstuvwxyz";
   $max = strlen($chars) - 1;
   mt_srand((double)microtime() * 1000000);
   for($i = 0; $i < $length; $i++)
   {
       $hash .= $chars[mt_rand(0, $max)];
   }
   return $hash;
}
//画干扰线的函数
function getLine($h){
for($j=0;$j<5;$j++){
//定义线条
$c_line = imagecolorallocate($h,rand(0,255),rand(0,255),rand(0,255));
//在图片上划线
imageline($h,rand(0,100),rand(0,30),rand(0,100),rand(0,30),$c_line);
}
}
//画噪点
function getPoint($h){
for($ii=0;$ii<400;$ii++){
$c_point = imagecolorallocate($h,rand(0,255),rand(0,255),rand(0,255));//定义噪点颜色
imagesetpixel($h,rand()%100,rand()%30,$c_point);
}
}
//画字符串
function paintString($h,$rd_str,$c_f){
imagestring($h,rand(4,6),rand(1,50),rand(1,15),$rd_str,$c_f);
}
 }
 $chek = new Check_Class();
?>