shell_exec is not working on server

shell_exec is not working on server

i am using shell_exec to get whois details of a domain. Everything is
working fine on localhost but when i am uploading the script on server, it
is creating problems. On server, the shell_exec is working partially.
echo "shell_exec('whoami')";
gives me an output.
mac
but when i am using
echo "shell_exec('whois example.com')";
I am getting a blank page
Should i consider using a hosting account with root privilege? If yes then
how to deal with security issues?
P.S- i dont know if something like this even exists but i've tested it on
localhost and it is running fine on MAMP.
Thanks in advance.