php微信支付v3版本签名生成

//生成v3 Authorization
    protected function createAuthorization( $url ){

        if (!in_array(‘sha256WithRSAEncryption‘, \openssl_get_md_methods(true))) {
            throw new \RuntimeException("当前PHP环境不支持SHA256withRSA");
        }
        $url_parts = parse_url($url);
        $canonical_url = ($url_parts[‘path‘] . (!empty($url_parts[‘query‘]) ? "?${url_parts[‘query‘]}" : ""));

        //私钥地址
        $mch_private_key = $this->mch_private_key;
        //商户号
        $merchant_id = $this->mch_id;
        //当前时间戳
        $timestamp =  time();
        //随机字符串
        $nonce = $this->createNoncestr();
        //POST请求时 
        $body =  $this->body ;
        $message = "GET\n".
            $canonical_url."\n".
            $timestamp."\n".
            $nonce."\n".
            $body."\n";

        //生成签名
        openssl_sign($message, $raw_sign, openssl_get_privatekey(file_get_contents($mch_private_key)), ‘sha256WithRSAEncryption‘);
        $sign = base64_encode($raw_sign);
        //Authorization 类型  
        $schema = ‘WECHATPAY2-SHA256-RSA2048‘;
        //生成token
        $token = sprintf(‘mchid="%s",serial_no="%s",nonce_str="%s",timestamp="%d",signature="%s"‘, $merchant_id,$this->serial_no, $nonce, $timestamp,  $sign);

        $header = [
            ‘Content-Type:application/json‘,
            ‘Accept:application/json‘,
            ‘User-Agent:*/*‘,
            ‘Authorization: ‘.  $schema . ‘ ‘ . $token
        ];
        return $header;
    }

/**
     *  作用：产生随机字符串，不长于32位
     */
    public function createNoncestr( $length = 32 )
    {
        $chars = "abcdefghijklmnopqrstuvwxyz0123456789";
        $str ="";
        for ( $i = 0; $i < $length; $i++ )  {
            $str.= substr($chars, mt_rand(0, strlen($chars)-1), 1);
        }
        return $str;
    }