WC_Connect_Service_Settings_Store::set_selected_payment_method_id PHP Method

        public function set_selected_payment_method_id($new_payment_method_id)
        {
            $new_payment_method_id = intval($new_payment_method_id);
            $account_settings = $this->get_account_settings();
            $old_payment_method_id = intval($account_settings['selected_payment_method_id']);
            if ($old_payment_method_id === $new_payment_method_id) {
                return;
            }
            $account_settings['selected_payment_method_id'] = $new_payment_method_id;
            $this->update_account_settings($account_settings);
        }

 protected function potentially_update_selected_payment_method_from_payment_methods($payment_methods)
 {
     $payment_method_count = count($payment_methods);
     // No payment methods at all? Clear anything we have stored
     if (0 === $payment_method_count) {
         $this->service_settings_store->set_selected_payment_method_id(0);
         return;
     }
     $payment_method_ids = array();
     foreach ((array) $payment_methods as $payment_method) {
         $payment_method_id = intval($payment_method->payment_method_id);
         if (0 !== $payment_method_id) {
             $payment_method_ids[] = $payment_method_id;
         }
     }
     // Just one? Go ahead and use it
     if (1 === $payment_method_count) {
         $this->service_settings_store->set_selected_payment_method_id($payment_method_ids[0]);
         return;
     }
     // Is the stored method id not in the list? Select the first one
     $selected_payment_method_id = $this->service_settings_store->get_selected_payment_method_id();
     if (!in_array($selected_payment_method_id, $payment_method_ids)) {
         $this->service_settings_store->set_selected_payment_method_id($payment_method_ids[0]);
     }
 }