Phpstorm How to associate multiple projects

This is the case, assuming that there are two projects, project A and project B;
Each time Phpstorm can only open one project, I first open project A, but project A has the source of the classes in Project B, but Phpstorm is not known.
How can I get the class in project A to be associated with the source code in Project B?

Do not let me put project A and project B in a folder, and then open in the Phpstorm oh. This approach is not the fundamental way to solve the problem.

Thank you, sir.

Reply content:

This is the case, assuming that there are two projects, project A and project B;
Each time Phpstorm can only open one project, I first open project A, but project A has the source of the classes in Project B, but Phpstorm is not known.
How can I get the class in project A to be associated with the source code in Project B?

Do not let me put project A and project B in a folder, and then open in the Phpstorm oh. This approach is not the fundamental way to solve the problem.

Thank you, sir.

Preference + + Project + Directories can configure multiple catalogs if two items are frequently modified to suggest this

The other is preference = language + PHP + include path can also be added to the directory, if a project is not often modified (class library, base library, etc.) recommend this

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