Acronym for Read The Fucking Source!

Usage is similar to RTFM; but implies that the solution to the problem at hand lies within the Source Code. On the other hand, basically anything to do with the program lies somewhere in the Source Code, but often the Source Code is so huge, it's like finding a needle in a haystack!

lib/main.php:944: Notice: PageInfo: Cannot find action page

lib/main.php:839: Notice: PageInfo: Unknown action