Including files issue with relative paths on a linux system

[PaulR]

I have the following directory tree structure:\[code\]/index.php/code/inc/variables.php/code/inc/config.php\[/code\]index.php is the file that is called.On our development system in: /code/inc/variables.php, when I have the line:\[code\]require_once("./code/inc/config.php");\[/code\]it doesnt work and when I have:\[code\]include_once('config.php');\[/code\]it does work.The puzzle is that the first works on our development system and the second works on our production system. And there is no difference in the tree structure on either of the two systems (both run linux, different versions perhaps).