A PHP verification code generation code

   class ValidationCode
   {
       //属性
       private $width;
       private $height;
       private $codeNum;
       private  $image;
       private $disturbColorNum;  //干扰元素数目
       private  $checkCode;
       function __construct($width=80,$height=20,$codeNum=4)
           {
           $this->width=$width;
           $this->height=$height;
           $this->codeNum=$codeNum;
           $number=floor($width*$height/15);
           if($number>240-$codeNum)
             {
               $this->disturbColorNum=240-$codeNum;
              }else
               {
                  $this->disturbColorNum=$number;
               }
               $this->checkCode=$this->createCheckcode();
       }
       function getCheckCode()
       {
           return $this->checkCode;
       }
       private function createImage(){
          $this->image=imagecreatetruecolor($this->width,$this->height);
          $backcolor=imagecolorallocate($this->image,rand(225,255),rand(225,255),rand(255,255));
          imagefill($this->image,0,0,$backcolor);
          $border=imagecolorallocate($this->image,0,0,0);
          imagerectangle($this->image,0,0,$this->width-1,$this->height-1,$border);
       }
       private function setDisturbColor(){
           for($i=0;$i<$this->disturbColorNum;$i++){
               $color=imagecolorallocate($this->image,rand(0,255),rand(0,255),rand(0,255));
              imagesetpixel($this->image,rand(1,$this->width-2),rand(1,$this->height-2),$color);
           }
           for($i=0;$i<10;$i++)
           {
                  $color=imagecolorallocate($this->image,rand(0,255),rand(0,255),rand(0,255));
                  imagearc($this->image,rand(-10,$this->width),rand(-10,$this->height),rand(30,300),rand(20,300),55,44,$color);
           }
       }
      private function outputText($fontFace=""){
          for($i=0;$i<$this->codeNum;$i++)
          {
              $fontcolor=imagecolorallocate($this->image,rand(0,128),rand(0,128),rand(0,128));
             if($fontFace=="")
            {
              $fontsize=rand(3,5);
              $x=floor($this->width/$this->codeNum)*$i+5;
              $y=rand(0,$this->height-15);
              imagechar($this->image,$fontsize,$x,$y,$this->checkCode{$i},$fontcolor);
             }
             else
            {
                 $fontsize=rand(12,16);
                 $x=floor(($this->width-8)/$this->codeNum)*$i+8;
                 $y=rand($fontsize,$this->height-8);
                 imagettftext($this->image,$fontsize,rand(-45,45),$x,$y,$fontcolor,$fontFace,$this->checkCode{$i});
             }
          }
      }

      private function createCheckCode(){
          $code="23456789abcdefghijkmnpqrstuvwrst";
          $str="";
          for($i=0;$i<$this->codeNum;$i++)
          {
              $char=$code{rand(0,strlen($code)-1)};
              $str.=$char;
          }
          return $str;
      }
      private function outputImage()
       {
          if(imagetypes()&IMG_GIF)
           {
             header("Content-Type:image/gif");
              imagepng($this->image);
           }else if(imagetypes()&IMG_JPG)
           {
                  header("Content-Type:image/jpeg");
                    imagepng($this->image);
           }else if(imagetypes()&IMG_PNG)
           {
                  header("Content-Type:image/png");
                  imagepng($this->image);
           }else if(imagetypes()&IMG_WBMP){
                 header("Content-Type:image/vnd.wap.wbmp");
                 imagepng($this->image);
           }else
           {
               die("PHP不支持图片验证码");
           }
       }
           //通过该方法向浏览器输出图像
       function  showImage($fontFace="")
       {
           //创建图像背景
            $this->createImage();
           //设置干扰元素
           $this->setDisturbColor();
           //向图像中随机画出文本
           $this->outputText($fontFace);
           //输出图像
           $this->outputImage();
       }

 function __destruct()
 {
 imagedestroy($this->image);
 }
 }
 function checklogin(){
 if(empty($_POST['name']))
 die( 'Username cannot is empty');
 if(empty($_POST['password']))
 die("Password cannot be empty");
 if($_SESSION['code']!=$_POST['vertify'])
 die("The verification code input is incorrect".$_SESSION['code']);

 $username=$_POST['name'];
 $password=md5($_POST['password']);
 / /Check if it exists
 conndb($username,$password);
 }
 function conndb($name="",$ps=""){
 $conn=mysql_connect('localhost','root','123456' );
 if(!$conn) die("Database connection failed".mysql_error());
 mysql_select_db('5kan',$conn) or die('Select database failed'.mysql_error());
 mysql_set_charset(' utf8',$conn);
 $sql="select id from k_user where username='{$name}' and password='{$ps}'";
 $result=mysql_query($sql) or die("SQL Statement error".mysql_error());
 if(mysql_num_rows($result)>0) die("Login successful");
 else die("Username or password is wrong");
 mysql_close($conn);
 }
 session_start();
 if(!isset($_POST['randnum']))
 {
 $code=new ValidationCode(120,20,4);
 $code->showImage("comicbd.ttf" ;

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