The "magic constants" of PHP

To Whom It May Concern, I'm not sure if you are the right people to ask about this, but I'm having a very hard time finding information about a particular aspect of PHP that is troubling me right now. They are something called "magic constants". Apparently, the use of the constants "__FILE__" and "__LINE__" are very common. The problem is, throughout the entire PHP.net web site, there is only one reference made to these "magic constants", and their mention is not very informative at all. See this page: http://www.php.net/manual/en/language.constants.php The only other references to "__FILE__" I could find, using Google on the PHP.net site, were in user comments, and they were only used in examples, so there was no clear definition of the use of these constants. After searching the web for any sort of definition for the magic constants, I finally found one at this page: http://www.sunsite.ualberta.ca/Documentation/Misc/php-3.0.15/language.constants.html In any case, the reason I was writing is because I just thought it would be a good idea to include a definition of this sort somewhere in the online documentation of PHP. If it is included somewhere that I haven't looked or wasn't able to find, then I apologize for the intrusion.