Questions about The require path

Ask the newbie about The require path. under the root directory, pay.domain.com is bound. ememberpay now. the PHP file under ememberpay requires that the require file be located in. in eclass, how can I write the path? it seems that a second-level domain name is troublesome for many new users to ask about The require path.
Www.domain.com is bound to the./root directory.

Pay.domain.com bound to./e/member/pay

Now the php file under./e/member/pay requires that the require file be located under./e/class

How to write the path

It seems a lot of trouble to have a second-level domain name.

Php require

------ Solution --------------------
The path on the server has little to do with the domain name, and is related to the file system.
The domain name is resolved externally and does not need to be considered internally.