验证码处理函数

<?php
include_once("global.php");
//===============================
class ValidationCode
{
    private $width,$height,$codenum;
    public $checkcode;     //产生的验证码
    private $checkimage;    //验证码图片
    private $disturbColor = ''; //干扰像素
    
    function ValidationCode($width='80',$height='20',$codenum='4')
    {
       $this->width=$width;
       $this->height=$height;
       $this->codenum=$codenum;
    }
    function outImg()
    {
       //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($this->checkimage);
    }
    private function outFileHeader()
    {
       ob_clean();
       header ("Content-type: image/png");
    }
    function GetfourStr($len) 
    { 
      $chars_array = array( 
        "1", "2", "3", "4", "5", "6", "7", "8", "9",
        "a", "b", "c", "d", "e", "f", "g", "h", "i", "j", "k", 
        "l", "m", "n", "p", "q", "r", "s", "t", "u", "v", 
        "w", "x", "y", "z", "A", "B", "C", "D", "E", "F", "G", 
        "H", "I", "J", "K", "L", "M", "N", "P", "Q", "R", 
        "S", "T", "U", "V", "W", "X", "Y", "Z", 
      ); 
      $charsLen = count($chars_array) - 1; 
      $outputstr = ""; 
      for ($i=0; $i<$len; $i++) 
      { 
        $outputstr .= $chars_array[mt_rand(0, $charsLen)]; 
      } 
      return $outputstr; 
    }
    private function createCode()
    {
       $this->checkcode = strtoupper($this->GetfourStr($this->codenum));
    }
    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
    }
    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);
        }
    }

    private function writeCheckCodeToImage()
    {
        for ($i=0;$i<$this->codenum;$i++)
        {
            $bg_color = imagecolorallocate ($this->checkimage, rand(0,255), rand(0,128), rand(0,255));
            $x = rand(0,7)+floor($this->width/$this->codenum)*$i;
            $y = rand(0,$this->height-15);
            imagechar ($this->checkimage, rand(5,8), $x, $y, $this->checkcode[$i], $bg_color);
        }
    }
    function __destruct()
    {
       unset($this->width,$this->height,$this->codenum);
    }
}
//===============================
$width=$_GET['w']?$_GET['w']:"80";
$height=$_GET['h']?$_GET['h']:"33";
$image = new ValidationCode($width,$height,'4'); 
$image->outImg();
$_SESSION["auth"] = $image->checkcode;
?>