PHP: long running process with closed connection

gistfile1.php

<?php

set_time_limit(0);
ignore_user_abort(TRUE);

// return the headers and close the connection, but keep running.
ob_start();

fJSON::output(array('success' => 'T', 'message' => 'The full synchronization process has started.'));
$length = ob_get_length();
header("Content-Length: $length");
header('Connection: close');
ob_end_flush();
ob_flush();
flush();

// if you're using sessions, this prevents subsequent requests
// from hanging while the background process executes
if (session_id()) session_write_close();

// do work...