$exec = exec("hostname"); //the "hostname" is a valid command in both windows and linux
$hostname = trim($exec); //remove any spaces before and after
$ip = gethostbyname($hostname); //resolves the hostname using local hosts resolver or DNS
$sock = socket_create(AF_INET, SOCK_DGRAM, SOL_UDP);
socket_connect($sock, "8.8.8.8", 53);
socket_getsockname($sock, $name); // $name passed by reference
// This is the local machine's external IP address
$localAddr = $name;