PHP生成验证码及单实例应用

/* note：
 * this     指向当前对象本身
 * self     指向当前类
 * parent   指向父类
 */

/* 验证码工具类
 * @author pandancode
 * @date 20150-12-1
 */
class Verification_Code{

    private $_vode;
    private $_vode_len;
    private $_img_handle;
    private $_img_width;
    private $_img_height;
    private $_img_type;
    private $_img_bg_color;
    private $_img_color;

    /* 单实例 */
    private static $_instance;

    /* 获取当前实例 */
    public static function getInstance(){
        if( !(self::$_instance instanceof self) ){
            self::$_instance = new self;
        }
        return self::$_instance;
    }

    /* 构造函数,设置 为private，禁止外部访问 */
    private function __Construct(){}

    /* 设置 为private，禁止外部访问,禁止外部访问 */
    private function __clone(){}

    /* 生成验证码图片前设置参数
     * @param string vode 验证码
     * @param int vode_len 验证码长度
     * @param string img_type 生成图片格式，默认为png
     */
    public function set_param($vode,$vode_len,$width,$height,$img_type='png',$img_bg_color=array('R'=>250,'G'=>'250','B'=>'250'),$img_color=array('R'=>0,'G'=>0,'B'=>0)){
        $this->_vode = $vode;
        $this->_vode_len = $vode_len;
        $this->_img_width = $width;
        $this->_img_height = $height;
        $this->_img_type = $_img_type;
        $this->_img_bg_color = $img_bg_color;
        $this->_img_color = $img_color;
    }

    /* 生成图片
     */
    public function create_img(){
        $this->_img_handle = ImageCreate($this->_img_width,$this->_img_height);
        $this->_img_bg_color = ImageColorAllocate($this->_img_handle,$this->_img_bg_color['R'],$this->_img_bg_color['G'],$this->_img_bg_color['B']);
        $this->_img_color = ImageColorAllocate($this->_img_handle,$this->_img_color['R'],$this->_img_color['G'],$this->_img_color['B']);

        //填充背景颜色
        Imagefill($this->_img_handle,0,0,$this->_img_bg_color);
        ImageString($this->_img_handle,10,10,10,$this->_vode,$this->_img_color);

        ob_clean();
        header('Content-type:image/png');
        Imagepng($this->_img_handle);
    }

}

$img_tool = Verification_Code::getInstance();
$img_tool->set_param('ABVS',4,80,40);
$img_tool->create_img();