Can't get list of users (roster) from xmpphp - php

Question

I have an app where I send xmpp message to some devices. This successfully works. But now I want to recieve roster (list of connected users) and I get empty array, however there are 4 users there. Here is my code
require_once($_SERVER["DOCUMENT_ROOT"]."/lib/xmpphp/XMPP.php");
$con=$conf->getXMPPObj();
try {
$con->useEncryption(false);
$con->connect();
$con->processUntil('session_start');
$con->presence();
$roster=$con->roster->getRoster();
var_dump($roster);
//$con->processUntil('roster_received');
if (strpos($_POST['msg'],'CamMode')!==false)
{
$con->message("user#host" ,$_POST['msg']);
}
else
{
$con->message("user#host",$_POST['msg']);
}
$con->disconnect();
}
catch(XMPPHP_Exception $e)
{
die($e->getMessage());
}
messages are successfully sent but dump of $roster is empty. What's wrong?

Answer 1

I add this : $con->processUntil(array('session_start', 'roster_received')); and $con->processTime(5); It worked for me.
...
$con->connect();
$payloads = $con->processUntil(array('session_start', 'roster_received'));
$con->presence();
$con->processTime(5);
$roster = $con->roster->getRoster();
...