How to allow command for www-data?

I try to execute the following PHP command to get the IP-adress from eth0.

$ip = trim(shell_exec("/sbin/ifconfig eth0 | grep -i 'inet Adresse:' | tr ':' ' ' | awk '{ print $3 }'"));

But i get nothing back. If i execute the exact same command via ssh then i get the IP, so the command should work.

I opened visudo and added these lines and restarted apache2 after it

www-data        ALL = NOPASSWD: /sbin/ifconfig
www-data        ALL = NOPASSWD: /bin/grep
www-data        ALL = NOPASSWD: /usr/bin/awk
www-data        ALL = NOPASSWD: /usr/bin/tr

But i still get nothing back