What does __FILE__ mean?

Question

I have the following code from Codeigniter index.php

My understanding is that,

If / of string position in $system_folder

Answer 1

1. The realpath() function gives you the file-system path, with any symbolic links and directory traversing (e.g. ../../) resolved. The dirname() function gives you just the directory, not the file within it.

2. __FILE__ is a magic constant that gives you the filesystem path to the current .php file (the one that __FILE__ is in, not the one it's included by if it's an include.

3. Sounds about right.

4. This is to translate from Windows style (\) paths to Unix style (/).