How to check if ssh tunnel is alive and externаl ip in one command?

Question

I'm connecting with phpsеclib like that:

<?php
include('Net/SSH2.php');

$ssh = new Net_SSH2('www.domain.tld');
if (!$ssh->login('username', 'password')) {
    exit('Login Failed');
}

echo $ssh->read('username@username:~$');
$ssh->write("some commands"); // here is the question
echo $ssh->read('username@username:~$');
?>

And I wаnt to check if my ssh still can tunnel traffic and get external ip.

By еxternal ip I mean the IP we will get after connection (sometimes it's different from IP tо which we connect).