PHP的中问验证码

<?php 
Class code 
{ 
 var $width =160; //图片的宽 
 var $hight =40; //图片的高 
 var $image; 
 var $red =223; //图片的RGB颜色 
 var $green =225; //红 
 var $blue =227 ;//绿 
 var $pix =227 ;//蓝 
 var $pixcolor; //杂色颜色; 
 var $pixred = 242; //红 
 var $pixgreen = 168;//绿 
 var $pixblue = 162; //蓝 
 var $txt=null;//验证码文字 
 var $txtcode=null; 
 var $txtsub=null; 
 var $pixnum = 300; //杂点数量 
 var $i=0; 
 var $widthpx=0; 
 var $highty=0; 
 var $txtreg=50; 
 var $txtgreen=30; 
 function createimage()  //创建一张图并填色 
 { 
  $this->image = imagecreate($this->width,$this->hight); 
  $this->color = imagecolorallocate($this->image,$this->red,$this->green,$this->blue); 
  return imagefill($this->image,0,0,$this->color); 
 } 
 function createpix() //干扰因素 
 { 
  for($this->i=1;$this->i<$this->pixnum;$this->i++) 
  { 
    $this->widthpx = rand(0,$this->width); 
    $this->highty = rand(0,$this->hight); 
   $this->pixcolor = imagecolorallocate($this->image,$this->pixred,$this->pixgreen,$this->pixblue); 
     imagesetpixel($this->image,$this->widthpx,$this->highty,$this->pixcolor); 
  } 
 } 
  function gettxt() //创建验证码文字 
 { 
  $this->txt = array("我","爱","你","叶","就","慧","明","发","真","的","很","想","不","知","到","为","什","么","就","是","忘","不","了","你","也","许","上","辈","欠","钱"); 
  for($this->i=0;$this->i<6;$this->i++) 
  { 
   $this->sub = $this->txt[rand(0,29)]; 
   $this->txtcode.= $this->sub; 
  } 
  $this->txtcode = iconv("GB2312","UTF-8",$this->txtcode); 
  $_SESSION["code"] = $this->txtcode; //产生的验证ID 
 } 
 function createstring() //创建验证码图片 
 { 
  imagettftext($this->image,20,5,0,40,$this->pixcolor,"C:\WINDOWS\Fonts\simsun.ttc ",$this->txtcode); 
  header("content-type:image/png"); 
  return imagepng($this->image); 
     imagedestroy($this->image); 
 } 
 function getcodeimage()//获得验证码图片 
 { 
  $this->createimage(); 
  $this->gettxt(); 
  $this->createpix();   
  $this->createstring(); 
 } 
} 
?> 
<?php  
session_start();    
$text = new code; 
$text->createimage(); 
$text->gettxt(); 
$text->createpix(); 
$text->createstring(); 
?>