How to generate verification code file in php

<?php
/**
* @file
* @version 1.0
* @author  网海浪子
* @brief   验证码文件类
*
*/
class CCheckCodeFile
{
//验证码位数
private $mCheckCodeNum = 4;
//产生的验证码
private $mCheckCode  = &#39;&#39;;
//验证码的图片
private $mCheckImage = &#39;&#39;;
//干扰像素
private $mDisturbColor = &#39;&#39;;
//验证码的图片宽度
private $mCheckImageWidth = &#39;80&#39;;
//验证码的图片宽度
private $mCheckImageHeight = &#39;20&#39;;
/**
*
* @brief  输出头
*
*/
private function OutFileHeader()
{
 header ("Content-type: image/png");
}
/**
*
* @brief  产生验证码
*
*/
private function CreateCheckCode()
{
 $this->mCheckCode = strtoupper(substr(md5(rand()),0,$this->mCheckCodeNum));
  return $this->mCheckCode;
}
 
/**
*
* @brief  产生验证码图片
*
*/
private function CreateImage()
{
 $this->mCheckImage = @imagecreate ($this->mCheckImageWidth,$this->mCheckImageHeight);
 imagecolorallocate ($this->mCheckImage, 200, 200, 200);
  return $this->mCheckImage;
}
/**
*
* @brief  设置图片的干扰像素
*
*/
private function SetDisturbColor()
{
  for ($i=0;$i<=128;$i++)
  {
  $this->mDisturbColor = imagecolorallocate ($this->mCheckImage, rand(0,255), rand(0,255), rand(0,255));
  imagesetpixel($this->mCheckImage,rand(2,128),rand(2,38),$this->mDisturbColor);
  }
}
/**
*
* @brief  设置验证码图片的大小
*
* @param  $width  宽
*
* @param  $height 高
*
*/
public function SetCheckImageWH($width,$height)
{
 if($width==&#39;&#39;||$height==&#39;&#39;)return false;
 $this->mCheckImageWidth = $width;
 $this->mCheckImageHeight = $height;
 return true;
}
/**
*
* @brief  在验证码图片上逐个画上验证码
*
*/
private function WriteCheckCodeToImage()
{
  for ($i=0;$i<=$this->mCheckCodeNum;$i++)
  {
  $bg_color = imagecolorallocate ($this->mCheckImage, rand(0,255), rand(0,128), rand(0,255));
  $x = floor($this->mCheckImageWidth/$this->mCheckCodeNum)*$i;
  $y = rand(0,$this->mCheckImageHeight-15);
  imagechar ($this->mCheckImage, 5, $x, $y, $this->mCheckCode[$i], $bg_color);
  }
}
/**
*
* @brief  输出验证码图片
*
*/
public function OutCheckImage()
{
 $this ->OutFileHeader();
 $this ->CreateCheckCode();
 $this ->CreateImage();
 $this ->SetDisturbColor();
 $this ->WriteCheckCodeToImage();
 imagepng($this->mCheckImage);
 imagedestroy($this->mCheckImage);
}
}
$c_check_code_image = new CCheckCodeFile();
//$c_check_code_image ->SetCheckImageWH(100,50);
//设置显示验证码图片的尺寸
$c_check_code_image ->OutCheckImage();
?>