Is it a Cookie setup problem?

[zzz]

I have a script that sets a cookie on login. The first function actually sets the cookie up, the second one checks if the person logged in:

function login ($username, $password) {
		if (!$username || !$password) {
                return $error;
		}
		else {
			if (!eregi("^[[:alnum:]_-]+$", $username)) {
				return $error
			}
			if (!eregi("^[[:alnum:]_-]+$", $password)) {
				return $error;
			}
			mysql_connect($this->server, $this->db_user, $this->db_pass);
			mysql_select_db($this->database);
			$query = mysql_query("select id from myTable where username = '$username' and password = '$password'");
			$result = @mysql_num_rows($query);
			mysql_close();
			if ($result < 1) {
				return false;
			}
			else {
				list ($id) = mysql_fetch_row($query);
				$hash = md5($username.$this->secret);
				setcookie("auth", "$username:$hash:$id", time()+3600, "/");
				return 2;
			}
		}
	}

function logged () {
		global $HTTP_COOKIE_VARS;
		$session_vars = explode(":", $HTTP_COOKIE_VARS['auth]);
		$hash = md5($session_vars[0].$this->secret);
		if ($hash != $session_vars[1]) {
			return false;
		}
		else {
			return array($session_vars[0], $session_vars[2]);
		}
	}

Recently I discovered that on some machines this does not work properly. I looked at the settings of that particular machine and see cookies from other sites, but not from my. Since I use this script from under HTTPS could there be a problem here somewhere? And if I had to rewrite the part dealing with cookies, how would I go about it without screwing up the current site?

[wilsonodk]

setcookie("auth", "$username:$hash:$id", time()+3600, "/");

Try this...

setcookie("auth","$username:$hash:$id",time()+3600,"/","[I]your domain[/I]",1);

I've found that filling out all the parameters helps the cookie work on every system.