Forum PHP.pl

Witam.

Napisałem owy skrypt mający na celu sprawdzanie użytkowników online.

[PHP] pobierz, plaintext 
<?php 
 
include ('engine/config.php');
include ('lang/en/bloks.php');
 
session_start();
 
	$time_now_uo = time();
	echo $time_now_uo . '<br />';
	$old_time_uo = time()-540;
 
	if (isset ($_SESSION['user_id'])) {
		$uidc = $_SESSION['user_id'];
		$sql_un = "SELECT username FROM " . $db_prefix . "users WHERE id='$uidc'";
		$un = mysqli_query($dbc, $sql_un);
		$username = mysqli_fetch_array($un);
		$unl = $username['username'];
 
			if($unl != false) { 
				$sql_uo_u = "UPDATE " . $db_prefix . "users_online SET time='$time_now_uo' WHERE username='$unl'";
				mysqli_query($dbc, $sql_uo_u);
			} else {
				$sql_uo_a = "INSERT INTO  " . $db_prefix . "users_online ('username' ,'time') VALUES ('$unl',  '$time_now_uo')";
				mysqli_query($dbc, $sql_uo_a);
			}
	}
 
	$sql_uo_d = "DELETE FROM " . $db_prefix . "users_online WHERE time < '$old_time_uo'";
	mysqli_query($dbc, $sql_uo_d);
 
	$sql_sun = "SELECT username FROM " . $db_prefix."users_online ORDER BY username";
	$sun = mysqli_query($dbc, $sql_sun);
	if (mysqli_num_rows($sun) != 0) { 
		echo $lang_bloks_bstats_uo . ': ';
		while($user_name = mysqli_fetch_array($sun)) { 
			echo $user_name['username'] . ', '; 
		}
	} else {
		echo $lang_bloks_bstats_nuo;
	}
 
?> 
[PHP] pobierz, plaintext 

Niestety nie zupełnie działa i nie wiem dlaczego... Czy ktoś mógłby zdefiniować co zrobiłem źle?

Baza:

[SQL] pobierz, plaintext 
CREATE TABLE `frycms`.`fry_users_online` (
`username` VARCHAR( 20 ) CHARACTER SET utf8 COLLATE utf8_unicode_ci NOT NULL ,
`time` INT NOT NULL ,
PRIMARY KEY ( `username` )
) ENGINE = MYISAM CHARACTER SET utf8 COLLATE utf8_unicode_ci;
[SQL] pobierz, plaintext 

Dzięki za pomoc.