Question

unlink("cache/data.xml");

I feel that this may generate an error at times when sever might be reading and serving it to the visitor.

how to safely delete the file so script will continue to wait until the read lock from the web server is released if any and then continue deleting the file or how it works out there?

Thanks

Answer 1

This will depend on the specific system this is running on, but the man page for the UNIX unlink function (which the PHP unlink function very likely relies on internally) says this:

The unlink() function removes the link named by path from its
directory and decrements the link count of the file which was
referenced by the link. If that decrement reduces the link count of
the file to zero, and no process has the file open, then all
resources associated with the file are reclaimed. If one or more
process have the file open when the last link is removed, the link is
removed, but the removal of the file is delayed until all references
to it have been closed.

In other words, the process reading the file can continue to do so, even while the file is being deleted.