How to establish a SSH local forward with PHP and connect to a remote DB afterwards

connect.php

<?php
$proc = new \Symfony\Component\Process\Process(
    '\\ssh -i ' . $pk . ' -NL 3307:' . $dbServ . ':3306 ' . $sshUsr . '@' . $sshHst . ' sleep 10 >> logfile'
);
$proc->start();

// wait until connection is established
sleep(1);
$dataBase = new \mysqli('127.0.0.1', $dbUsr, $dbPwd, $dbName, 3307);
$result = false;
if ($dataBase->errno === 0) {
    $query = $dataBase->query('show databases');
    $result = $query->fetch_all(MYSQLI_ASSOC);
}

// !!! This does not destroy the port forwarding !!!
$proc->stop();
return $result;