PHP provides a number of 'magic constants' such as __LINE__, __FILE__, __FUNCTION__, __CLASS__ and __METHOD__. Use this tag with questions tagged [php] that ask about these, and any other, magic constants.
If your question is about PHP (so it has a php tag) and is also intrinsically about one of the magic constants in PHP, then you can use this tag.
Examples of such magic constants include:
__LINE____FILE____FUNCTION____CLASS____METHOD____DIR__
Etc.
