Checking exec() runs successfully or not

Question

I have been trying to let know know if the exec() command in php executes successfully or not so i can echo certain messages accordingly. I tried the following

Answer 1

The correct way is to check that the $return_var was not set to zero because it is only set to zero when it is successful. In certain cases the exec can fail and the return_var is not set to anything. E.g. if the server ran out of disk space during the exec.

Note : do not initialize $return_var to zero