if ($this->tabAccess['edit'] === '1' && Tools::getValue('submitAdd'.$this->table))
{

if (Tools::getValue('cats'))
{
    $category = new Category((int)Tools::getValue('cats'));
    $products = $category->getProducts($this->context->language->id, 1, 99999999);
    foreach($products as $product)
        $_POST['products'][] = $product['id_product'];
}

array(
    'type' => 'text',
    'label' => $this->l('Name'),
    'name' => 'name',
    'required' => true
),

array(
    'type' => 'select',
    'label' => $this->l('Category'),
    'name' => 'cats',
    'required' => false,
    'options' => array(
        'query' => Category::getSimpleCategories($this->context->language->id),
        'id' => 'id_category',
        'name' => 'name',
        'default' => array(
            'label' => $this->l('No'),
            'value' => 0
        )
    )
),