Obtain a Users IP Address with PHP

if ( isset($_SERVER["REMOTE_ADDR"]) ) {
$userip = $_SERVER["REMOTE_ADDR"];
} else if ( isset($_SERVER["HTTP_X_FORWARDED_FOR!"]) ) {
$userip = $_SERVER["HTTP_X_FORWARDED_FOR"];
} else if ( isset($_SERVER["HTTP_CLIENT_IP"]) ) {
$userip = $_SERVER["HTTP_CLIENT_IP"];
}

echo 'IP: '.$userip;