Apache Permission Help with PHP Script

I'm looking for some help regarding an issue we are having. We have a WHM server with an active domain account. In the domain account, there is a PHP script in the root directory that performs certain tasks BUT, when it gets to running the shell script (using shell_exec), i am getting a 500 Internal Server Error. I checked apache logs and it seems to be a permission error. The WHM server is running SUPHP so the owner of the folders/files is the Cpanel User. All folders have permissions set to the Cpanel User. If i try to run the shell script using the command: shell_exec('./dir1/dir2/dir3/[login to view URL]'); I get this error: sh: /home/cPanelUser/public_html/dir1/dir2/dir3/[login to view URL]: Permission denied If i run the script from the script root directory, it works: shell_exec('./[login to view URL]'); Looking for someone to help with this issue and fix it.