int filectime (string filename)
Returns the time the file was last changed, or false in case of an error. The time is returned as a Unix timestamp.
The results of this function are cached. See clearstatcache() for more details.
Note: In most Unix filesystem, a file is considered changed, when it's Inode data is changed, that is, when the permissions, the owner, the group or other metadata from the Inode is written to. See also filemtime() (this is what you want to use when you want to create "Last Modified" footers on web pages) and fileatime().
Note: In some Unix texts the ctime of a file is being referred to as the creation time of the file. This is wrong. There is no creation time for Unix files in most Unix filesystems.