• wechatpay-apache-httpclient，适用于使用Apache HttpClient处理HTTP的Java开发者。
• wechatpay-guzzle-middleware，适用于PHP开发者。

这里用的是PHP，所以使用 wechatpay-guzzle-middleware 。

// 该文件复制自 \vendor\wechatpay\wechatpay-guzzle-middleware\tool

下载微信支付平台证书主要文件 CertificateDownloader.php

 <?php

namespace App\Http\Controllers\WxPay;
// 该文件复制自 \vendor\wechatpay\wechatpay-guzzle-middleware\tool\CertificateDownloader.php

use Illuminate\Http\Request;
use App\Http\Controllers\Controller;

use GuzzleHttp\HandlerStack;
use GuzzleHttp\Handler\CurlHandler;
use GuzzleHttp\Client;
use GuzzleHttp\Exception\RequestException;
use WechatPay\GuzzleMiddleware\WechatPayMiddleware;
use WechatPay\GuzzleMiddleware\Validator;
use WechatPay\GuzzleMiddleware\Util\PemUtil;
use WechatPay\GuzzleMiddleware\Util\AesUtil;
use WechatPay\GuzzleMiddleware\Auth\CertificateVerifier;
use WechatPay\GuzzleMiddleware\Auth\WechatPay2Validator;

class CertificateDownloader extends Controller
{
    const VERSION = '0.1.0';

    public function index() {
        $opts=[
            'mchid'=> config('globaldatas.mchid'),
            'serialno'=> config('globaldatas.serial_no'),
            'privatekey'=> "apiclient_cert.pem",
            'wechatpay-cert'=> null,
            'key'=> config('globaldatas.apiv'),
            'output'=> '微信平台证书存放目录'
        ];
        $this->downloadCert($opts);
    }

    public function run()
    {
        $opts = $this->parseOpts();
        if (!$opts) {
            $this->printHelp();
            exit(1);
        }

        if (isset($opts['help'])) {
            $this->printHelp();
            exit(0);
        }
        if (isset($opts['version'])) {
            echo self::VERSION . "\n";
            exit(0);
        }

        $this->downloadCert($opts);
    }

    private function parseOpts()
    {
        $opts = [
            [ 'key', 'k', true ],
            [ 'mchid', 'm', true ],
            [ 'privatekey', 'f', true ],
            [ 'serialno', 's', true ],
            [ 'output', 'o', true ],
            [ 'wechatpay-cert', 'c', false ],
        ];

        $shortopts = 'hV';
        $longopts = [ 'help', 'version' ];
        foreach ($opts as $opt) {
            $shortopts .= $opt[1].':';
            $longopts[] = $opt[0].':';
        }
        $parsed = getopt($shortopts, $longopts);
        if (!$parsed) {
            return false;
        }

        $args = [];
        foreach ($opts as $opt) {
            if (isset($parsed[$opt[0]])) {
                $args[$opt[0]] = $parsed[$opt[0]];
            }
            else if (isset($parsed[$opt[1]])) {
                $args[$opt[0]] = $parsed[$opt[1]];
            }
            else if ($opt[2]) {
                return false;
            }
        }

        if (isset($parsed['h']) || isset($parsed['help'])) {
            $args['help'] = true;
        }
        if (isset($parsed['V']) || isset($parsed['version'])) {
            $args['version'] = true;
        }
        return $args;
    }

    private function printHelp()
    {
        echo <<<EOD
Usage: 微信支付平台证书下载工具 [-hV] [-c=<wechatpayCertificatePath>]
                    -f=<privateKeyFilePath> -k=<apiV3key> -m=<merchantId>
                    -o=<outputFilePath> -s=<serialNo>
  -m, --mchid=<merchantId>   商户号
  -s, --serialno=<serialNo>  商户证书的序列号
  -f, --privatekey=<privateKeyFilePath>
                             商户的私钥文件
  -k, --key=<apiV3key>       ApiV3Key
  -c, --wechatpay-cert=<wechatpayCertificatePath>
                             微信支付平台证书，验证签名
  -o, --output=<outputFilePath>
                             下载成功后保存证书的路径
  -V, --version              Print version information and exit.
  -h, --help                 Show this help message and exit.

EOD;
    }
}

downloadCert 方法

同级PHP文件 NoopValidator.php