PHP:: relative paths in include() or require()

While this might seem fairly obvious, I'd still like to point out that PHP's functions include(), include_once(), require() and require_once() have problems including files in different directories where paths of the filenames are relative. The absolute path of the included files is generated from the filename of the first included file, so any relative path in the second nested include will not have relative paths starting from it's directory, but the directory of the first file. To avoid confusion I find it's best to use absolute paths with the magic constant __FILE__, which is always the current script's filename.

Example:

require_once(dirname(__FILE__).'/../../include_all.php');