PHP including files -

what's difference between

$_server['document_root']; 

and

dirname(__file__); 

i wonder what's difference because when 'echo' them, they're returning same path. prefer should use , why?

thanks!

both different

_file_

the full path , filename of file. if used inside include, name of included file returned. since php 4.0.2, file contains absolute path symlinks resolved whereas in older versions contained relative path under circumstances.

source : php magic constants

let's said, document /var/www,
, index page /var/www/index.php

dirname(__file__) == $_server['document_root']; 

but if drill-down sub-folder /var/www/posts/index.php

dirname(__file__) != $_server['document_root']; /var/www/posts    != /var/www 

the use of $_server['document_root'] more appropriate in case.