Something

function print_folders($folder = ""){

	global $imap;
	
	if($folder = ""){

		$list = imap_getmailboxes($imap, "{localhost:143}", "%");
		
		foreach ($list as $key => $val) {
		
		}
	
	} else{
	
		$list = imap_getmailboxes($imap, "{localhost:143}".$folder."", "%");
		
		foreach ($list as $key => $val) {
		
		}
	
	}

}