Auto (categories)
     Peugeot ===> 208 (sub categories)
     Color  ===> black

Material
     Plastic ===> Yes
     Cuir    ===> Yes

Auto
    Peugeot ===> 208
    Renault   ===> 208   ==> no good value. it must not appear not included
    Color ===> black
    Color   ===> black   ==> no good value. it must not appear not included

Materials
    Plastic ===> Yes
    Cuir    ===> Yes

$QSpecification = $this->db->prepare('select ag.specification_group_id,
                                                      agd.name,
                                                      pa.products_id
                                              from :table_products_specification pa,
                                                   :table_specification a,
                                                   :table_products_specification_group ag,
                                                   :table_products_specification_group_description agd
                                              where pa.products_id = :products_id
                                              and agd.language_id = :language_id
                                              and pa.customers_group_id = :customers_group_id
                                              and pa.specification_group_id = a.specification_group_id
                                              and a.specification_group_id = ag.specification_group_id
                                              and ag.specification_group_id = agd.specification_group_id
                                              and pa.status = 1
                                              group by ag.specification_group_id
                                              order by ag.sort_order,
                                                      agd.name
                                              ');
        $QSpecification->bindInt(':products_id', $products_id);
        $QSpecification->bindInt(':language_id', $this->lang->getId());
        $QSpecification->bindInt(':customers_group_id', $this->customer->getCustomersGroupID());

        $QSpecification->execute();

        $specification = $QSpecification->fetchAll();

foreach ($specification as $product_specification_group) {
          $product_specification_data = [];

          $QproductsSpecification = $this->db->prepare('select pa.specification_group_id,
                                                                a.specification_id,
                                                                pa.id,
                                                                ad.name,
                                                                pad.text
                                                        from  :table_products_specification_description pad,
                                                         :table_products_specification pa,
                                                         :table_specification a,
                                                        :table_specification_description ad

                                                        where pa.products_id = :products_id
                                                        and a.specification_group_id = :specification_group_id
                                                        and a.specification_id = ad.specification_id
                                                        and pa.specification_group_id = a.specification_group_id
                                                        and ad.language_id = :language_id
                                                        and pad.language_id = :language_id
                                                        and pa.id = pad.id
                                                        and (pa.customers_group_id = :customers_group_id or pa.customers_group_id = 99)
                                                        and pa.status = 1
                                                        order by pa.sort_order,
                                                                ad.name
                                                                ');

          $QproductsSpecification->bindInt(':specification_group_id', $product_specification_group['specification_group_id']);
          $QproductsSpecification->bindInt(':language_id', $this->lang->getId());
          $QproductsSpecification->bindInt(':products_id', $products_id);
          $QproductsSpecification->bindInt(':customers_group_id', $this->customer->getCustomersGroupID());

          $QproductsSpecification->execute();

$product_specification_data[] = ['specification_id' => $QproductsSpecification->valueInt('specification_id'),
      'name' => $QproductsSpecification->value('name'),
      'text' => $QproductsSpecification->value('text')
    ];
    }
  }


  $product_specification_group_data[] = ['specification_group_id' => $product_specification_group['specification_group_id'],
    'name' => $product_specification_group['name'],
    'specification' => $product_specification_data
  ];
}

    var_dump($product_specification_group_data);