On macOS there is a tool called fs_usage which can be used to see what files are accessed on the system while it is running. It needs sudo to run.
ps aux | grep php-fpmsudo fs_usage -f "pathname" [pid]access checks whether the calling process can access the file pathnameopen creates a new open file description, an entry in the system-wide table of open filesclose closes a file descriptorstat64 returns information about a file