PHP验证码

代码如下：

<?php
    class Imagecode{
        private $width ;
        private $height;
        private $counts;
        private $distrubcode;
        private $fonturl;
        private $session;
        function __construct($width = 120,$height = 30,$counts = 5,$distrubcode="1235467890qwertyuipkjhgfdaszxcvbnm",$fonturl="C:\Windows\Fonts\simfang.ttf"){
            $this->width=$width;
            $this->height=$height;
            $this->counts=$counts;
            $this->distrubcode=$distrubcode;
            $this->fonturl=$fonturl;
            $this->session=$this->sessioncode();
            session_start();
            $_SESSION['code']=$this->session;
        }

         function imageout(){
            $im=$this->createimagesource();
            $this->setbackgroundcolor($im);
            $this->set_code($im);
            $this->setdistrubecode($im);
            ImageGIF($im);
            ImageDestroy($im);
        }

        private function createimagesource(){
            return imagecreate($this->width,$this->height);
        }
        private function setbackgroundcolor($im){
            $bgcolor = ImageColorAllocate($im, rand(200,255),rand(200,255),rand(200,255));//±??°????
            imagefill($im,0,0,$bgcolor);
        }
        private function setdistrubecode($im){
            $count_h=$this->height;
            $cou=floor($count_h*2);
            for($i=0;$i<$cou;$i++){
                $x=rand(0,$this->width);
                $y=rand(0,$this->height);
                $jiaodu=rand(0,360);
                $fontsize=rand(8,15);
                $fonturl=$this->fonturl;
                $originalcode = $this->distrubcode;
                $countdistrub = strlen($originalcode);
                $dscode = $originalcode[rand(0,$countdistrub-1)];
                $color = ImageColorAllocate($im, rand(40,140),rand(40,140),rand(40,140));
                imagettftext($im,$fontsize,$jiaodu,$x,$y,$color,$fonturl,$dscode);

            }
        }
        private function set_code($im){
                $width=$this->width;
                $counts=$this->counts;
                $height=$this->height;
                $scode=$this->session;
                $y=floor($height/2)+floor($height/4);
                $fontsize=rand(30,35);
                $fonturl="C:\Windows\Fonts\simfang.ttf";//$this->fonturl;

                $counts=$this->counts;
                for($i=0;$i<$counts;$i++){
                    $char=$scode[$i];
                    $x=floor($width/$counts)*$i+8;
                    $jiaodu=rand(-20,30);
                    $color = ImageColorAllocate($im,rand(0,50),rand(50,100),rand(100,140));
                    imagettftext($im,$fontsize,$jiaodu,$x,$y,$color,$fonturl,$char);
                }



        }
        private function sessioncode(){
                $originalcode = $this->distrubcode;
                $countdistrub = strlen($originalcode);
                $_dscode = "";
                $counts=$this->counts;
                for($j=0;$j<$counts;$j++){
                    $dscode = $originalcode[rand(0,$countdistrub-1)];
                    $_dscode.=$dscode;
                }
                return $_dscode;

        }
    }
    Header("Content-type: image/GIF");
    $imagecode=new Imagecode(160,50);
    $imagecode->imageout();