exit status of ./a.out (c compiled code) on running it

Question

I have ac compiled code.
I am using

exec('./a.out 2>&1',$out,$ret);

in my php script to get return type where I want to know first whether it ran fine or what went wrong a segmentation fault or infinite loop or something like that.
basically i want to know the exit status 0,1 and 2 and there significance.
if any other exit status exist please tell those also..

Answer 1

PHP puts the exit status of the exec()ed program to the $ret variable. The program has exited successfully iff $ret becomes 0 after exec() returns.