WC_Order::payment_complete PHP Method

    public function payment_complete($transaction_id = '')
    {
        try {
            if (!$this->get_id()) {
                return false;
            }
            do_action('woocommerce_pre_payment_complete', $this->get_id());
            if (!empty(WC()->session)) {
                WC()->session->set('order_awaiting_payment', false);
            }
            if ($this->has_status(apply_filters('woocommerce_valid_order_statuses_for_payment_complete', array('on-hold', 'pending', 'failed', 'cancelled'), $this))) {
                $order_needs_processing = false;
                if (sizeof($this->get_items()) > 0) {
                    foreach ($this->get_items() as $item) {
                        if ($item->is_type('line_item') && ($product = $item->get_product())) {
                            $virtual_downloadable_item = $product->is_downloadable() && $product->is_virtual();
                            if (apply_filters('woocommerce_order_item_needs_processing', !$virtual_downloadable_item, $product, $this->get_id())) {
                                $order_needs_processing = true;
                                break;
                            }
                        }
                    }
                }
                if (!empty($transaction_id)) {
                    $this->set_transaction_id($transaction_id);
                }
                $this->set_status(apply_filters('woocommerce_payment_complete_order_status', $order_needs_processing ? 'processing' : 'completed', $this->get_id()));
                $this->set_date_paid(current_time('timestamp'));
                $this->save();
                do_action('woocommerce_payment_complete', $this->get_id());
            } else {
                do_action('woocommerce_payment_complete_order_status_' . $this->get_status(), $this->get_id());
            }
        } catch (Exception $e) {
            return false;
        }
        return true;
    }

 public function process_payment($order_id)
 {
     global $woocommerce;
     $me = wp_get_current_user();
     $order = new WC_Order($order_id);
     if ($me->ID == 0) {
         $woocommerce->add_error(__('Payment error:', 'woothemes') . __('You must be logged in to use this payment method', 'wc_account_funds'));
         return;
     }
     $funds = get_user_meta($me->ID, 'account_funds', true);
     if (!$funds) {
         $funds = 0;
     }
     if ($funds < $order->order_total) {
         $woocommerce->add_error(__('Payment error:', 'woothemes') . __('Insufficient account balance', 'wc_account_funds'));
         return;
     }
     // Payment complete
     $order->payment_complete();
     // deduct amount from account funds
     $new_funds = $funds - $order->order_total;
     update_user_meta($me->ID, 'account_funds', $new_funds);
     // Remove cart
     $woocommerce->cart->empty_cart();
     // Return thank you page redirect
     if (method_exists($order, 'get_checkout_order_received_url')) {
         return array('result' => 'success', 'redirect' => $order->get_checkout_order_received_url());
     } else {
         return array('result' => 'success', 'redirect' => add_query_arg('key', $order->order_key, add_query_arg('order', $order_id, get_permalink(get_option('woocommerce_thanks_page_id')))));
     }
 }