Passed the test and there were questions that I did not understand.
What is __ used for (most likely these are two underscores)? Answer - used to refer to magical methods is not true. That's the question for what else.
_____ (probably four underscores) is used for validation and cleanup: $ _REQUEST or $ _SERVER or $ _GET or $ _COOKIES. In the Internet, I do not find something like that. Explain
__DIR__- ArchDemon