きれいなPHP認証コード類

<?php
//    
class ValidateCode {
private $charset = 'abcdefghkmnprstuvwxyzABCDEFGHKMNPRSTUVWXYZ23456789';    //    
    private $code;                            //   
    private $codelen = 4;                    //     
    private $width = 130;                    //  
    private $height = 50;                    //  
    private $img;                                //      
    private $font;                                //     
    private $fontsize = 20;                //      
    private $fontcolor;                        //      


    //       
    public function __construct() {
        $this->font = ROOT_PATH.'/font/elephant.ttf';
    }


    //     
    private function createCode() {
        $_len = strlen($this->charset)-1;
        for ($i=0;$i<$this->codelen;$i++) {
            $this->code .= $this->charset[mt_rand(0,$_len)];
        }
    }


    //    
    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);
    }


    //    
    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),$_x*$i+mt_rand(1,5),$this->height / 1.4,$this->fontcolor,$this->font,$this->code[$i]);
        }
    }


    //    、  
    private function createLine() {
        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,$this->height),mt_rand(0,$this->width),mt_rand(0,$this->height),$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);
        }
    }


    //  
    private function outPut() {
        header('Content-type:image/png');
        imagepng($this->img);
        imagedestroy($this->img);
    }


    //    
    public function doimg() {
        $this->createBg();
        $this->createCode();
        $this->createLine();
        $this->createFont();
        $this->outPut();
    }


    //     
    public function getCode() {
        return strtolower($this->code);
    }
}