由此提问展开的步骤验证，亲测可用。 安装wechatpay-php包 [代码]composer require wechatpay/wechatpay [代码] 查看 composer 版本 执行 [代码]composer -V [代码] 打印出 [代码]Composer version 2.1.5 2021-07-23 10:35:47 [代码] 查询当前可用命令 执行 [代码]composer exec -l [代码] 打印出 [代码]Available binaries: - CertificateDownloader.php [代码] 平台证书下载工具帮助信息 执行 [代码]composer exec CertificateDownloader.php [代码] 打印出 [代码]Usage: 微信支付平台证书下载工具 [-hV] -f=<privateKeyFilePath> -k=<apiv3Key> -m=<merchantId> -s=<serialNo> -o=[outputFilePath] -u=[baseUri] Options: -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> APIv3密钥 -o, --output=[outputFilePath] 下载成功后保存证书的路径，可选，默认为临时文件目录夹 -u, --baseuri=[baseUri] 接入点，可选，默认为 https://api.mch.weixin.qq.com/ -V, --version Print version information and exit. -h, --help Show this help message and exit. [代码] 下载 执行 [代码]composer exec CertificateDownloader.php -- -m 你的商户号 -s 40字节你的商户证书序列号 -f 你的apiclient_key.pem文件路径 -k 你的APIv3密钥 -o . [代码] 打印出 [代码]* Trying 101.226.137.13:443... * Connected to api.mch.weixin.qq.com (101.226.137.13) port 443 (#0) * ALPN, offering http/1.1 * SSL connection using TLSv1.2 / ECDHE-RSA-AES256-GCM-SHA384 * ALPN, server accepted to use http/1.1 * Server certificate: * subject: C=CN; ST=Guangdong Province; L=Shenzhen; O=Shenzhen Tencent Computer Systems Company Limited; CN=payapp.weixin.qq.com * start date: Jan 5 00:00:00 2021 GMT * expire date: Feb 4 23:59:59 2022 GMT * subjectAltName: host "api.mch.weixin.qq.com" matched cert's "api.mch.weixin.qq.com" * issuer: C=US; O=DigiCert Inc; CN=DigiCert Secure Site CN CA G3 * SSL certificate verify ok. > GET /v3/certificates HTTP/1.1 Host: api.mch.weixin.qq.com Accept: application/json, text/plain, application/x-gzip Content-Type: application/json; charset=utf-8 User-Agent: wechatpay-php/1.1.3 GuzzleHttp/7 curl/7.78.0 (Darwin/17.7.0) PHP/7.2.34 Authorization: WECHATPAY2-SHA256-RSA2048 mchid="你的商户号",serial_no="40字节你的商户证书序列号",timestamp="1629856192",nonce_str="VUQqkOgKn6IQNnBZenJ9qodfI0CSYMeD",signature="s9oLRyuX4Y4Eb4fG9ZOz8dPutHmnnJAniNkTk/tpFGbAfo9fEDAGIepHpCbSKkthlAcOewdijHeYorEnn6TfJmixCxZU9M1A4YLE1tCVZ5Vu7gVpYOc6T94fi/9ZjPh0P6ql7xwkHvFJelE306ttx27JggbmmfOsYfHUfDROXqsbPXDIphCMGCzIqPTxa2f+RainXduVreHU7D2MB33GCf0B1uCfUSDS0K1mVOyMl4tYpGUx83PWlceCaw823Flse2ZTVoRta/p5dAT+CCi3vLgJ1kTv6sfEONvBXkCS7CM7V7iKcACgxzOaq/5aiHd7f4peXPs8eYlrmFAvNXs/jQ==" * Mark bundle as not supporting multiuse < HTTP/1.1 200 OK < Server: nginx < Date: Wed, 25 Aug 2021 01:49:54 GMT < Content-Type: application/json; charset=utf-8 < Content-Length: 2168 < Connection: keep-alive < Keep-Alive: timeout=8 < Cache-Control: no-cache, must-revalidate < X-Content-Type-Options: nosniff < Request-ID: 08C2C39689061490011889DFEEA30620F23528FB06-0 < Content-Language: zh-CN < Wechatpay-Nonce: 384dadb556fb2baf92b2d4c1b07b7ae9 < Wechatpay-Signature: OnHwA+dXZr1CWKH1RtzTKftzc9i+arjMk/3vSkBfuP8H/txqRDcuppt0ZVQac4Tnzmy1wSwAYoeuFS9OfH0UKtLDx1XJCKhNxdgzGDaOY7FgQ+s9Y7SD7/41d2Yd3YiqA1FRjXw29liLQ8hwzqdjhv6F6ShU6m4Tp3oe99W/HvvK1QuQwlDqGfPl+bbtyNpbdYzI3I0fq3AW/USshxi5GH0ipf4VEGgSCH3iEXRbnu/zOnv4PneHS1OgAWTtRMsNcHa4orwQIk9JyTeR/ea4O3ts44WQWV4B8+eRGEyNyWnehEfbJuA6Wa6c3pU4NyPCxSjIrFw7qzUj7vvo1wn6hw== < Wechatpay-Timestamp: 1629856194 < Wechatpay-Serial: samples < * Connection #0 to host api.mch.weixin.qq.com left intact Certificate #0 { Serial Number: 平台证书序列号 Not Before: 2020-04-22T09:43:19+08:00 Not After: 2025-04-21T09:43:19+08:00 Saved to: ./平台证书文件.pem You may confirm the above infos again even if this library already did(by Crypto\Rsa::verify): openssl x509 -in ./平台证书文件.pem -noout -serial -dates Content: -----BEGIN CERTIFICATE----- MIID3DCCAsSgAwIBAgIUGpn29Q2WYL6wG3Qd+V5Yh2DSN1MwDQYJKoZIhvcNAQEL BQAwXjELMAkGA1UEBhMCQ04xEzARBgNVBAoTClRlbnBheS5jb20xHTAbBgNVBAsT FFRlbnBheS5jb20gQ0EgQ2VudGVyMRswGQYDVQQDExJUZW5wYXkuY29tIFJvb3Qg Q0EwHhcNMjAwNDIyMDE0MzE5WhcNMjUwNDIxMDE0MzE5WjBuMRgwFgYDVQQDDA9U AQfkCW7DNT7iU6oQK+sMTxjiZwMBIqKOWsxvO8ljEpndHkCKXbmd/xKv54o5Pbam Ta7YQKocLOM7N96/9zasjV9OVVUktazq9XQoReki1EKnbhZvLoS5L5ECbVB/VIwL Qok2zZVOm81GwKe0r7tb+gPO6c0K2/XiVpJd5w9PO6M= -----END CERTIFICATE----- } [代码] 至此，[代码]\WeChatPay\Builder::factory([])[代码]所需的[代码]平台证书序列号[代码]及[代码]平台证书文件.pem[代码]就下载完成了。