Front End-Multiple sets of PHP open source systems, user integration issues

Many small sites, get a set of web systems, will generally use, bbs,cms,shop and other open source products. Suppose that there are many sets of open source systems in the program. How are users managed?
1. Data unification
This is the first problem to face, different systems have their own user table, this should be how to do? To become a total management center, or separate still use their own management center, if you want to unify the complete user table, is manual in the direction of the table to organize it?
2. Login Management Issues
If you do a login on the CMS, BBS also to log in once, assuming that the BBS did a registration, CMS inside no this user ...

This kind of question, do not know how everybody solves?

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Many small sites, get a set of web systems, will generally use, bbs,cms,shop and other open source products. Suppose that there are many sets of open source systems in the program. How are users managed?
1. Data unification
This is the first problem to face, different systems have their own user table, this should be how to do? To become a total management center, or separate still use their own management center, if you want to unify the complete user table, is manual in the direction of the table to organize it?
2. Login Management Issues
If you do a login on the CMS, BBS also to log in once, assuming that the BBS did a registration, CMS inside no this user ...

This kind of question, do not know how everybody solves?

Discuz's ucenter scheme can be considered

can refer to Ucenter, but if the integration is not good, security is a problem.

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