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

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

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