I have Ghostscript and IMagemagick installed on my local machine. I can access the IM functions from the command line. The environment variables are also set.

The problem is that when I try to execute the IM function using PHP's exec() method, I get no result. The same script works on my remote web host.
When the execution is successful, exec() returns a 0. On my local machine, it returns 4.

Is there a way to see any kind of error message returned from exec()? How do I know that PHP is able to find IM?

Any help in this matter would be useful!