class f2fpayService
{
    protected $appId;
    protected $notifyUrl;
    //私钥文件路径
//    protected $rsaPrivateKeyFilePath;
    //私钥值
    protected $rsaPrivateKey;

    public function __construct($appid, $notifyUrl, $saPrivateKey)
    {
        $this->appId = $appid;
        $this->notifyUrl = $notifyUrl;
        $this->charset = 'utf8';
        $this->rsaPrivateKey = $saPrivateKey;
    }

    /**
     * 发起订单
     * @param float $totalFee 收款总费用 单位元
     * @param string $outTradeNo 唯一的订单号
     * @param string $orderName 订单名称
     * @param string $notifyUrl 支付结果通知url 不要有问号
     * @param string $timestamp 订单发起时间
     * @return array
     */
    public function doPay($totalFee, $outTradeNo, $orderName, $notifyUrl)
    {
        //请求参数
        $requestConfigs = array(
            'out_trade_no' => $outTradeNo,
            'total_amount' => $totalFee, //单位 元
            'subject' => $orderName, //订单标题
        );
        $commonConfigs = array(
            //公共参数
            'app_id' => $this->appId,
            'method' => 'alipay.trade.precreate',       //接口名称
            'format' => 'JSON',
            'charset' => $this->charset,
            'sign_type' => 'RSA2',
            'timestamp' => date('Y-m-d H:i:s'),
            'version' => '1.0',
            'notify_url' => $notifyUrl,
            'biz_content' => json_encode($requestConfigs),
        );
        $commonConfigs["sign"] = $this->generateSign($commonConfigs, $commonConfigs['sign_type']);
        $result = $this->curlPost('https://openapi.alipay.com/gateway.do', $commonConfigs);
        return json_decode($result, true);
    }

    public function generateSign($params, $signType = "RSA")
    {
        return $this->sign($this->getSignContent($params), $signType);
    }

    protected function sign($data, $signType = "RSA")
    {
        $priKey = $this->rsaPrivateKey;
        $res = "-----BEGIN RSA PRIVATE KEY-----\n" .
            wordwrap($priKey, 64, "\n", true) .
            "\n-----END RSA PRIVATE KEY-----";
        ($res) or die('您使用的私钥格式错误，请检查RSA私钥配置');
        if ("RSA2" == $signType) {
            openssl_sign($data, $sign, $res, version_compare(PHP_VERSION, '5.4.0', '<') ? SHA256 : OPENSSL_ALGO_SHA256); //OPENSSL_ALGO_SHA256是php5.4.8以上版本才支持
        } else {
            openssl_sign($data, $sign, $res);
        }
        $sign = base64_encode($sign);
        return $sign;
    }

    /**
     * 校验$value是否非空
     * if not set ,return true;
     *  if is null , return true;
     **/
    protected function checkEmpty($value)
    {
        if (!isset($value))
            return true;
        if ($value === null)
            return true;
        if (trim($value) === "")
            return true;
        return false;
    }

    public function getSignContent($params)
    {
        ksort($params);
        $stringToBeSigned = "";
        $i = 0;
        foreach ($params as $k => $v) {
            if (false === $this->checkEmpty($v) && "@" != substr($v, 0, 1)) {
                // 转换成目标字符集
                $v = $this->characet($v, $this->charset);
                if ($i == 0) {
                    $stringToBeSigned .= "$k" . "=" . "$v";
                } else {
                    $stringToBeSigned .= "&" . "$k" . "=" . "$v";
                }
                $i++;
            }
        }
        unset ($k, $v);
        return $stringToBeSigned;
    }

    /**
     * 转换字符集编码
     * @param $data
     * @param $targetCharset
     * @return string
     */
    private function characet($data, $targetCharset)
    {
        if (!empty($data)) {
            $fileType = $this->charset;
            if (strcasecmp($fileType, $targetCharset) != 0) {
                $data = mb_convert_encoding($data, $targetCharset, $fileType);
                //$data = iconv($fileType, $targetCharset.'//IGNORE', $data);
            }
        }
        return $data;
    }

    private function curlPost($url = '', $postData = '', $options = array())
    {
        if (is_array($postData)) {
            $postData = http_build_query($postData);
        }
        $ch = curl_init();
        curl_setopt($ch, CURLOPT_URL, $url);
        curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
        curl_setopt($ch, CURLOPT_POST, 1);
        curl_setopt($ch, CURLOPT_POSTFIELDS, $postData);
        curl_setopt($ch, CURLOPT_TIMEOUT, 30); //设置cURL允许执行的最长秒数
        if (!empty($options)) {
            curl_setopt_array($ch, $options);
        }
        //https请求 不验证证书和host
        curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, false);
        curl_setopt($ch, CURLOPT_SSL_VERIFYHOST, false);
        $data = curl_exec($ch);
        curl_close($ch);
        return $data;
    }


    public function verify($data, $sign, $alipayPublicKey, $signType = 'RSA')
    {

        $pubKey = $alipayPublicKey;

        $res = "-----BEGIN PUBLIC KEY-----\n" .
            wordwrap($pubKey, 64, "\n", true) .
            "\n-----END PUBLIC KEY-----";

        ($res) or die('支付宝RSA公钥错误。请检查公钥文件格式是否正确');

        //调用openssl内置方法验签，返回bool值

        if ("RSA2" == $signType) {
            $result = (bool)openssl_verify($data, base64_decode($sign), $res, OPENSSL_ALGO_SHA256);
        } else {
            $result = (bool)openssl_verify($data, base64_decode($sign), $res);
        }
        return $result;
    }
}

转自：https://blog.hidove.cn/post/732