Form inside foreach loop php

I'm struggling with a problem.

I have a foreach inside another foreach -that's not the problem- what happens is that, when I try to put a form inside the nested foreach, my controller doesn't react. When I click on the "+" button it's supposed to add the order and then redirect me to somewhere.php, otherwise, it should redirect me to nowhere.php. It just doesn't redirect me nowhere -without the .php, haha-, meaning that the isset($_POST['do_add'} is not working.

Any ideas?

My controller:

<?php 
    $br = new Brand;
    $ord = new Order;
    $temp = new Template('templates/menu.php');
    $temp->br = $br->getAllBrands();
    $temp->car = new Car;
    echo $temp;
    if(isset($_POST['do_add'])) {
        $idPlate = $_POST['idCars'];
        if ($ped->addCar($idCar)) { 
            redirect('somewhere.php');
        } else {
            redirect('nowhere.php');
        }
    } 
?>

My template:

<table class = "table">
<?php foreach ($brands as $brand): ?>
    <thead class = "thead-inverse">
        <tr>
            <th> <?php echo $brand->name; // these are just some car brands ?> </th>
        </tr>
    </thead>
    <?php foreach ($cars->getCars($brand->idBrands) as $car): // here I get all the cars ordered by brands ?>
    <tbody>
        <form role = "form" method = "post" action = "carList.php">
            <tr>
                <td name = "idCar" value = "<?php echo $car->idCars; ?>"><p><?php echo $car->model; ?></p></td>
                <td>
                    <button name = "do_add" type = "submit">+</button>
                </td>
            </tr>
        </form>
    </tbody>
    <hr>
    <?php endforeach; ?>
<?php endforeach; ?>
</table> 

Thank you!