我正在使用兩個查詢從我的數據庫中獲取，當我嘗試在每個查詢中打印結果時，它確實打印了所有結果，但是當我嘗試在外部打印時，它并沒有打印所有內容：$arr_devices = [];$sql1 = "SELECT id FROM users WHERE users.name = '$company_name'"; //finding the ids of the users of this companyif ($res = $db->query($sql1)) {    $arr_id = $res->fetch_all(MYSQLI_ASSOC);    foreach ($arr_id as $company_id) {        $sql = "SELECT        devices.id,         devices.serial_imei,         devices.serial_no,         devices.type_id,         devices.cus_id,         devices.sales_date,        device_types.name,        device_types.manufacturer,        device_types.device_no,        device_types.barcode,        users.id,        users.name as manufacturer_name        FROM devices        INNER JOIN device_types         ON device_types.id = devices.type_id        INNER JOIN users ON device_types.manufacturer = users.id        WHERE devices.cus_id = " . $company_id['id'] . " ";        $result = $db->query($sql);        if ($result->num_rows > 0) {            $arr_devices = $result->fetch_all(MYSQLI_ASSOC);        }        print_r($arr_devices);  //HERE IT PRINTS EVERYTHING I AM FETCHING    }    print_r($arr_devices);  //HERE IT DOESNT}