The pathinfo() function is designed to take a filename and return the same filename broken into various components. It takes a filename as its only parameter, and returns an array with three elements: dirname, basename, and extension. Dirname contains the name of the directory the file is in (e.g. "c:\windows" or "/var/www/public_html"), basename contains the base filename (e.g. index.html, or somefile.txt), and extension contains the file extension if any (e.g. "html" or "txt").
If all you want to do is get the filename part of a path, you can use the basename() function. This takes a path as its first parameter, and, optionally, an extension as its second parameter. The return value from the function is the name of the file without the directory information. If the filename has the same extension as the one you specified in parameter two, the extension is taken off also.