$combination = '1/2/3/2/3/1/1/3/2/4/5/6/5/6/4/4/6/5/';
    $combination .= '7/8/9/8/9/7/7/9/8/1/4/7/4/7/1/1/7/4/';
    $combination .= '2/5/8/5/8/2/2/8/5/3/6/9/6/9/3/3/9/6/';
    $combination .= '1/5/9/5/9/1/1/9/5/2/5/7/5/7/2/2/7/5';

    $moves = array_chunk(explode('/', $combination), 3);
    foreach ($moves as $move) {
        if ($_SESSION['board'][$move[0]] == 'x' && $_SESSION['board'][$move[1]] == 'x' && $_SESSION['board'][$move[2]] == '') {
            unset($_SESSION['_board'][$move[2]]);
            $_SESSION['board'][$move[2]] = 'o';
            header("Location: index.php");
            exit();
        }
    }