A good PHP captcha class instance to share

Share a handy php captcha class, including a sample call.
Description:
If the specified font does not apply, use the imagestring() function, or imagettftext() function if you need to encounter the specified font. The font position is Windows/Fonts under C disk.

This paper refers to the method of php generating captcha on the Internet, as well as the generation method of php image captcha and php Chinese captcha. The PHP GD library is used.

1. VerificationCode. class. php class to generate captcha

<?php  
    class VerificationCode{  
        private $charset="abcdefghjkmnpqrstuvwxyzABCDEFGHJKMNPQRSTUVWXYZ23456789";  // The random factor   
        private $code;  // Verification code   
        private $codelen=4; // Captcha length   
        private $width=110; // The width of the   
        private $height=30; // highly   
        private $img;   // Image resource handle   
        private $font;  // Set the font   
        private $fontSize=25;   // The font size   
        private $fontColor; // The font color   
        public function __construct(){  
            $this->font="CALIBRIZ.TTF";  
        }  
        // Generate verification code   
        private function createCode(){  
            $len=strlen($this->charset)-1;  
            for ($i = 0; $i < $this->codelen; $i++) {  
                $this->code .= $this->charset[mt_rand(0,$len)];  
            }  
        }  
        // Generate the background   
        private function createBg(){  
            $this->img=imagecreatetruecolor($this->width,$this->height);  
            $color = imagecolorallocate($this->img,mt_rand(157,255),mt_rand(157,255),mt_rand(157,255));  
            imagefilledrectangle($this->img,0,$this->height,$this->width,0,$color);  
        }  
        // Generate text   
        private function createFont(){  
            $x=$this->width/$this->codelen;  
            for ($i = 0; $i < $this->codelen; $i++) {  
                $this->fontColor=imagecolorallocate($this->img,mt_rand(0,156),mt_rand(0,156),mt_rand(0,156));  
                imagettftext($this->img,$this->fontSize,mt_rand(-30,30),$i*$x+mt_rand(1,5),$this->height/1.4,$this->fontColor,$this->font,$this->code[$i]);  // www.ofstack.com
                //imagestring($this->img,5,$i*$x+mt_rand(1,5),5,$this->code[$i],$this->fontColor);  
            }  
        }  
        // Generate lines, snowflakes   
        private function createDisturb(){  
            for ($i = 0; $i < 6; $i++) {  
                $color=imagecolorallocate($this->img,mt_rand(0,156),mt_rand(0,156),mt_rand(0,156));  
                imageline($this->img,mt_rand(0,$this->width),mt_rand(0,$this->width),mt_rand(0,$this->width),mt_rand(0,$this->width),$color);  
            }  
            for ($i = 0; $i < 100; $i++) {  
                $color=imagecolorallocate($this->img,mt_rand(200,255),mt_rand(200,255),mt_rand(200,255));  
                imagestring($this->img,mt_rand(1,5),mt_rand(0,$this->width),mt_rand(0,$this->height),'*',$color);  
            }  
        }  
        // The output   
        private function outPut(){  
            header("Content-Type:image/png");  
            imagepng($this->img);  
            imagedestroy($this->img);  
        }  
        public function showCode(){  
            $this->createBg();  
            $this->createCode();  
            $this->createDisturb();  
            $this->createFont();  
            $this->outPut();  
        }  
        // Get verification code   
        public function getCode(){  
            return strtolower($this->code);  
        }  
    }  
?>

code.php

<?php  
    session_start();  
    require_once 'VerificationCode.class.php';  
    $code=new VerificationCode();  
    $_SESSION['code']=$code->getCode();  
    $code->showCode();  
?>  
 Verification code :<input type="text" name="code" /><img src="code.php" onclick="javascript:this.src='code.php?time='+Math.random();" />