syscall and rexec

Hi, I'm having some problems in using php's system calls, (system, exec, passthru, and even popen) to run the following command. rexec <machine> ls That fails with no output. I know what username apache uses to run the php script, and despite being able to rexec from the command line using that user id, apache seems to have trouble when it comes to running it self. Even though I can rexec from the command line I've still confirmed that the correct username and password are inside the .netrc file, and as a final confirmation I've checked that no environment variables are set, no -n in the command line or username and password specified. Has anyone has been able to get this to work, or knows a little about how the system call and exec call work inside php that might aid me in getting this script to work? Many thanks, Mostafa