When developing a WeChat official account, what unique identifier can be obtained in the background?

For example, this WeChat account has very good benefits. If you are afraid that others will receive more, you can just log in to N accounts with your mobile phone to receive it.
Can I get some other information to identify, mac, or mobile phone serial number?

I have only learned PHP, JS, etc. sporadically, and have not done anything practical yet. I am asking this just to get acquainted with it.
I hope everyone can explain it in a simple and in-depth way. A few words will be enough. The more the better, thank you! ! !

Reply content:

For example, this WeChat account has very good benefits. If you are afraid that others will receive more, you can just log in to N accounts with your mobile phone to receive it.
Can I get some other information to identify, mac, or mobile phone serial number?

I have only learned PHP, JS, etc. sporadically, and have not done anything practical yet. I am asking this just to get acquainted with it.
I hope everyone can explain it in a simple and in-depth way. A few words will be enough. The more the better, thank you! ! !

1. Every user on WeChat has his or her own unique ID

2. Due to permissions, not every official account can obtain the user's ID, so the users followed under each official account also have the user's unique ID corresponding to the official accountcalled openid

3. Many official accounts have the function of binding WeChat ID to the official account system account. In fact, it is obvious that users have unique IDs.

4. In web auth authorization, silent authorization can obtain very few permissions. Only when the user confirms authorization can the user's ID, avatar, region, signature and other information be obtained.

You can use openid to distinguish it in WeChat