It seems that the include path are not considered as files.
is_file($autoexec) returns false

I changed this:
--- inc file ----
$autoexec = "auto.bat";
$path = "\n%path%=%path%;c:\php\php.exe";
----

> --- snip ----
require_once('paths.inc');

function updateFichier(){
global $autoexec, $path;
> if (!$myBool = fopen ($autoexec, "a")) {
> echo "Cant create($autoexec)";
> exit;
> }
>
> The include file is printed on screen
> The function exit with Cant create the file