I'm writing a photo gallery script in PHP and have a single directory where the user will store their pictures. I'm attempting to set up page caching and have the cache refresh only if the contents of the directory has changed. I thought I could do this by caching the last modified time of the directory using the filemtime() function and compare it to the current modified time of the directory. However, as I've come to realize, the directory modified time does not change as files are added or removed from that directory (at least on Windows, not sure about Linux machines yet).
So my questions is, what is the simplest way to check if the contents of a directory have been modified?
Uh. I'd simply store the md5 of a directory listing. If the contents change, the md5(directory-listing) will change. You might get the very occasional md5 clash, but I think that chance is tiny enough..
Alternatively, you could store a little file in that directory that contains the "last modified" date. But I'd go with md5.
PS. on second thought, seeing as how you're looking at performance (caching) requesting and hashing the directory listing might not be entirely optimal..