1.把微信公众号和微信小程序绑定到微信开放平台后，在微信公众号的这个接口（https://api.weixin.qq.com/sns/userinfo?access_token=" . $access_token . "&openid=" . $openid . "&lang=zh_CN）以及微信小程序的这个接口（https://api.weixin.qq.com/sns/jscode2session）会增加一个unionid字段。

需要注意绑定微信公众号以及微信小程序都是 同主体50个，不同主体5个。下面我列举下接口返回数据

小程序：
通过code换取：
{"code":200,"msg":"ok","info":{"session_key":"KTmrpRTKUrfFQUYynqOiRA==","openid":"oHAXV4oOV5OdgqDtkqRvjuy6MIoU","unionid":"oO91ywTkYDiGVMN633V1GDiTCeus"},"xcx_config":{"appid":"wxb38096deb66b049f","xcx_name":"多选一经销端
{"code":200,"msg":"ok","info":{"session_key":"JWPosf+W6FQF\/B3vQtSurA==","expires_in":7200,"openid":"oszsa0Tlqo0uKKsl9jWWmYVIeNlE","unionid":"oO91ywTkYDiGVMN633V1GDiTCeus"},"xcx_config":{"appid":"wxbe34ed1bdfe9d9f9","xcx_name":"菜鸟工具tool"}}


公众号：
获取用户信息接口会多返回unionid
https://api.weixin.qq.com/sns/userinfo?access_token=" . $access_token . "&openid=" . $openid . "&lang=zh_CN

{"openid":"o1vEwt5XTvmUiYsaSBiNcJld9ni8","nickname":"\u5a03\u5a03\u83dc\ud83c\udde8\ud83c\uddf3","sex":0,"language":"","city":"","province":"","country":"","headimgurl":"https:\/\/thirdwx.qlogo.cn\/mmopen\/vi_32\/Iia5gMS7EgLlkhj8EtNaUbuRkpn1YDJTMTHhSompicwwZJ2gzCibibIxxNzWxD1iboXmQ6qzPgx7w9krff2A4yZPV3xxfeJz4k4M15M5cwO1HQdM\/132","privilege":[],"unionid":"oO91ywTkYDiGVMN633V1GDiTCeus"}