/**
	 * 取得支付寶簽名
	 *
	 * @return string
	 */
	private function sign($parameter) {
		$mysign = "";
		
		$filtered_array	= $this->para_filter($parameter);
		$sort_array = $this->arg_sort($filtered_array);
		$arg = "";
        while (list ($key, $val) = each ($sort_array)) {
			$arg	.= $key."=".$this->charset_encode($val,(empty($parameter['_input_charset'])?"UTF-8":$parameter['_input_charset']),(empty($parameter['_input_charset'])?"UTF-8":$parameter['_input_charset']))."&";
		}
		$prestr = substr($arg,0,-1);  //去掉最後一個&號
		$prestr	.= $parameter['key'];
        if($parameter['sign_type'] == 'MD5') {
			$mysign = md5($prestr);
		}elseif($parameter['sign_type'] =='DSA') {
			//DSA 簽名方法待後續開發
			die("DSA 簽名方法待後續開發，請先使用MD5簽名方式");
		}else {
			die("支付寶暫不支援".$parameter['sign_type']."型別的簽名方式");
		}
		return $mysign;
	}

	/**
	 * 除去陣列中的空值和簽名模式
	 *
	 * @param array $parameter
	 * @return array
	 */
	private function para_filter($parameter) {
		$para = array();
		while (list ($key, $val) = each ($parameter)) {
			if($key == "sign" || $key == "sign_type" || $key == "key" || $val == "")continue;
			else	$para[$key] = $parameter[$key];
		}
		return $para;
	}

	/**
	 * 重新排序引數陣列
	 *
	 * @param array $array
	 * @return array
	 */
	private function arg_sort($array) {
		ksort($array);
		reset($array);
		return $array;
	}


	/**
	 * 實現多種字元編碼方式
	 */
	private function charset_encode($input,$_output_charset,$_input_charset="UTF-8") {
		$output = "";
		if(!isset($_output_charset))$_output_charset  = $this->parameter['_input_charset'];
		if($_input_charset == $_output_charset || $input == null) {
			$output = $input;
		} elseif (function_exists("mb_convert_encoding")){
			$output = mb_convert_encoding($input,$_output_charset,$_input_charset);
		} elseif(function_exists("iconv")) {
			$output = iconv($_input_charset,$_output_charset,$input);
		} else die("sorry, you have no libs support for charset change.");
		return $output;
	}

  	/**
     * 製作支付介面的請求地址
     *
     * @return string
     */
    private function create_url() {
		$url        = $this->alipay_gateway_new;
		$filtered_array	= $this->para_filter($this->parameter);
		$sort_array = $this->arg_sort($filtered_array);
		$arg        = "";
		while (list ($key, $val) = each ($sort_array)) {
			$arg.=$key."=".urlencode($val)."&";
		}
		$url.= $arg."sign=" .$this->parameter['sign'] ."&sign_type=".$this->parameter['sign_type'];
		return $url;
	}