imap_createmailbox($mbox, imap_utf7_encode("{imap.example.org}INBOX.Test"));
imap_createmailbox($mbox, imap_utf7_encode("{imap.example.org}INBOX.haha"));
imap_createmailbox($mbox, imap_utf7_encode("{imap.example.org}INBOX.Test.hehe"));
imap_createmailbox($mbox, imap_utf7_encode("{imap.example.org}INBOX.Test.hehe.huhu"));
imap_createmailbox($mbox, imap_utf7_encode("{imap.example.org}INBOX.miav"));


function print_mailboxes($start = ""){

	//print $start;
	global $mbox;
	
	$list = imap_getmailboxes($mbox, "{localhost:143/novalidate-cert}$start", "%");
	
	if (is_array($list)) {
	    foreach ($list as $key => $val) {
		   $name = str_replace("{localhost:143/novalidate-cert}$start", "", $val->name);
		   print $name."<br>";
			if (!($val->attributes & LATT_HASNOCHILDREN)) {
				if($start = ""){
					$next = $start . ".";
					
				} else{
					$next = $start;
				}
				print_mailboxes($next . $name);
			}
			echo "<br />\n";
	    }
	}
}

the output of print_mailboxes is:

INBOX
.Test

INBOX.miav

INBOX.haha