CRITICAL - 2025-07-10 00:58:46 --> [Caused by] mysqli_sql_exception: Cannot add or update a child row: a foreign key constraint fails (ospos115.ospos_giftcards, CONSTRAINT ospos_giftcards_ibfk_1 FOREIGN KEY (person_id) REFERENCES ospos_people (person_id))
in SYSTEMPATH\Database\MySQLi\Connection.php on line 327.
1 SYSTEMPATH\Database\MySQLi\Connection.php(327): mysqli->query('INSERT INTO ospos_giftcards (record_time, giftcard_number, value, person_id) VALUES ('2025-07-10 00:58:45', '23', 45, '0')', 0)
2 SYSTEMPATH\Database\BaseConnection.php(738): CodeIgniter\Database\MySQLi\Connection->execute('INSERT INTO ospos_giftcards (record_time, giftcard_number, value, person_id) VALUES ('2025-07-10 00:58:45', '23', 45, '0')')
3 SYSTEMPATH\Database\BaseConnection.php(652): CodeIgniter\Database\BaseConnection->simpleQuery('INSERT INTO ospos_giftcards (record_time, giftcard_number, value, person_id) VALUES ('2025-07-10 00:58:45', '23', 45, '0')')
4 SYSTEMPATH\Database\BaseBuilder.php(2345): CodeIgniter\Database\BaseConnection->query('INSERT INTO ospos_giftcards (record_time, giftcard_number, value, person_id) VALUES (:record_time:, :giftcard_number:, :value:, :person_id:)', [...], false)
5 APPPATH\Models\Giftcard.php(145): CodeIgniter\Database\BaseBuilder->insert([...])
6 APPPATH\Controllers\Giftcards.php(131): App\Models\Giftcard->save_value([...], -1)
7 SYSTEMPATH\CodeIgniter.php(933): App\Controllers\Giftcards->postSave(-1)
8 SYSTEMPATH\CodeIgniter.php(507): CodeIgniter\CodeIgniter->runController(Object(App\Controllers\Giftcards))
9 SYSTEMPATH\CodeIgniter.php(354): CodeIgniter\CodeIgniter->handleRequest(null, Object(Config\Cache), false)
10 SYSTEMPATH\Boot.php(334): CodeIgniter\CodeIgniter->run()
11 SYSTEMPATH\Boot.php(67): CodeIgniter\Boot::runCodeIgniter(Object(CodeIgniter\CodeIgniter))
12 FCPATH\index.php(56): CodeIgniter\Boot::bootWeb(Object(Config\Paths))

I wonder how this would have worked then , I don't see any changes to gitcard table since some time. Did you use mariadb or mysql for the test?

I use Mysql and to get this option to work I had to drop the constraint. And in Controller /Sales the following needs to be modified if a Customer needs to be added to the Sale with a blank Giftcard name otherwise you get the Incorrect Customer Error.
I did get the following to work as I hoped it would. if (isset($cur_giftcard_customer) && $cur_giftcard_customer != $customer_id && $cur_giftcard_customer != 0)

if (isset($cur_giftcard_customer) && $cur_giftcard_customer != $customer_id) {
                    $data['error'] = lang('Giftcards.cannot_use', [$giftcard_num]);
                } elseif (($cur_giftcard_value - $current_payments_with_giftcard) <= 0 && $this->sale_lib->get_mode() === 'sale') {
                    $data['error'] = lang('Giftcards.remaining_balance', [$giftcard_num, $cur_giftcard_value]);
                } else {
                    $new_giftcard_value = $giftcard->get_giftcard_value($giftcard_num) - $this->sale_lib->get_amount_due();
                    $new_giftcard_value = max($new_giftcard_value, 0);
                    $this->sale_lib->set_giftcard_remainder($new_giftcard_value);
                    $new_giftcard_value = str_replace('$', '\$', to_currency($new_giftcard_value));
                    $data['warning'] = lang('Giftcards.remaining_balance', [$giftcard_num, $new_giftcard_value]);
                    $amount_tendered = min($this->sale_lib->get_amount_due(), $giftcard->get_giftcard_value($giftcard_num));

                    $this->sale_lib->add_payment($payment_type, $amount_tendered);
                }

Its weird as the foreign key seems to have been there for some time, so maybe mysql behavior changed and it cannot be null anymore? Thanks for the suggestion I might apply it to the master

Might be related to #4306, giftcards that do not have any customer linked might not work now unless we add this change you suggested @odiea

I haven't looked at the code for this change, but from a use standpoint I think the use of a giftcard should not require the purchasing customer to be entered, but I can see arguments either way for requiring a customer to be entered in the sales register. In terms of fraud prevention, having the purchasing and using customers be stored. We could make a "Require customer to use gift cards" checkbox so that those who want to track gift card use with a specific customer can enforce it.

I think it will be incredibly important to test database schema changes against both MariaDB and MySQL.