How to set the path of the files/folders when creating an archive

Hello,
I am trying to add some folders when creating a zip file, but unfortunately I can't figure out how can I set the path or the directories content.
To summarize the issue $zip->zip_add(__DIR__ . "/myfiles/"); puts the files and folders in the root of the zip file, in my case I want to put them under myfiles/ folder inside the zip file.

Thank you!