unique User_ID

how to assign a unique_id to each user during logon and how to retrieve it?

I’m trying to add the ‘uniqid()’ function into ‘insert_register_form.php’ in the plugin folder. But how do I use the value from the function to assign to a new field? Ideally it’ll come up as an un-editable text box in the registration page along with the other fields such as first name etc.

I also have had a look at the ‘Get_User_ID()’ function in ‘public_functions.php’ file but how do you access that and how does it work?

finally if there is more documentation/api please let me know.

Many Thanks

https://ww.wp.xz.cn/plugins/front-end-only-users/