Prestashop 1.6.1.14 - 数据库查询在Execute上返回1

Question

I am currently using the code below in Prestashop to retrieve a cart id.

    public function hookDisplayPDFInvoice($params) {

    $order_invoice = $params['object'];
    $id_order = (int)$order_invoice->id_order;

    $sql = 'SELECT id_cart FROM '._DB_PREFIX_.'orders WHERE id_order="'.$id_order.'"';
    //example id_cart
    $id_cart = Db::getInstance()->execute($sql);
    return $id_cart;

In database, there are id_cart and id_timeslot. Table is called ps_cart_timeslot.

I am quite stuck as I am baffled as to why the data return is 1 for any data I am retrieving.

$id_order is fine, it is returning the right value. Any data select I am querying will return 1.

Am I missing anything? Pardon me if this is a silly mistake.

Thank you.

Answer 1

For selects use Db::getInstance()->executeS($sql); or to get single value use Db::getInstance()->getValue($sql);

However since PS 1.6 you should be using query builder.

$query = new DbQuery();
$query->select('id_cart')
      ->from('orders')
      ->where('id_order = ' . (int)$id_order);
Db::getInstance(_PS_USE_SQL_SLAVE_)->getValue($query);
// Or array of values
Db::getInstance(_PS_USE_SQL_SLAVE_)->executeS($query);

execute() method returns only true or false while executeS() will return an array of select results (method can only be used for select queries) and getValue() will return the first value found in result.