验证码类，生成验证码

class Captcha{
    private $charset = ‘abcdefghkmnprstuvwxyzABCDEFGHKMNPRSTUVWXYZ23456789‘;    //随机因子，
    private $code;                     //验证码字符串
    private $codelen = 4;              //验证码长度
    private $width = 150;              //宽度
    private $height = 40;              //高度
    private $img;                      //图形资源句柄
    private $font;                     //指定的字体
    private $fontsize = 20;            //指定字体大小
    private $fontcolor;                //指定字体颜色

//构造方法初始化
    public function __construct($codelen=4,$width=150,$height=40,$fontsize = 20,$font="elephant.ttf") {
        $this->codelen = $codelen;
        $this->width = $width;
        $this->height = $height;
        $this->fontsize = $fontsize;
        $this->font = $font;
    }

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

//生成背景
    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);
    }

//生成文字
    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]);
        }
    }

//生成线条、雪花
    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);
        }
    }

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

//对外生成
    public function generateCode() {
        $this->createBg();
        $this->createCode();
        $this->createLine();
        $this->createFont();
        $this->outPut();
    }

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

//调用实例
//$c = new Captcha();
//$c->generateCode();
//$_SESSION[‘captcha‘] = $c->getCode();