GaryK - 6:02 pm on Oct 26, 2012 (gmt 0)
I'm not sure what the change does.
In Unix-like operating systems, /dev/null or the null device is a special file that discards all data written to it (but reports that the write operation succeeded) and provides no data to any process that reads from it (yielding EOF immediately).
Could the file change itself.
I'm not sure about PHP, but in most cases with the right permissions on a file it can be modified by anyone/anything.