R help - Apr 2004 - R , apache and PHP

I've developed a web application in PHP and R

my script is


<?php

...
exec("R CMD BATCH --silent /home/marcello/R_in/myfile.bat  
/home/marcello/R_out/myfile.out");

...

?>

This script execute in R batch mode and write the myfile.out.

On Win2000 the similar script is ok, but on linux I've a problem.

I suppose is a permession problem because the same script on shell run fine
and on Zend debugger (my IDE for php) is also ok.
In this case the owner is "marcello" , if I run the script by browser 
the owner is "apache".

I've  overwritted all the ownerships of R directory and bin to apache 
user but not work.

If a run
exec("ls > mydir.txt"); is ok (is not a PHP general problem!)

Someone can help me?

Thanks
(and excuse my for my poor english)

Marcello Verona