WC_REST_Posts_Controller::create_item PHP Method

    public function create_item($request)
    {
        if (!empty($request['id'])) {
            /* translators: %s: post type */
            return new WP_Error("woocommerce_rest_{$this->post_type}_exists", sprintf(__('Cannot create existing %s.', 'woocommerce'), $this->post_type), array('status' => 400));
        }
        $post = $this->prepare_item_for_database($request);
        if (is_wp_error($post)) {
            return $post;
        }
        $post->post_type = $this->post_type;
        $post_id = wp_insert_post($post, true);
        if (is_wp_error($post_id)) {
            if (in_array($post_id->get_error_code(), array('db_insert_error'))) {
                $post_id->add_data(array('status' => 500));
            } else {
                $post_id->add_data(array('status' => 400));
            }
            return $post_id;
        }
        $post->ID = $post_id;
        $post = get_post($post_id);
        $this->update_additional_fields_for_object($post, $request);
        // Add meta fields.
        $meta_fields = $this->add_post_meta_fields($post, $request);
        if (is_wp_error($meta_fields)) {
            // Remove post.
            $this->delete_post($post);
            return $meta_fields;
        }
        /**
         * Fires after a single item is created or updated via the REST API.
         *
         * @param object          $post      Inserted object (not a WP_Post object).
         * @param WP_REST_Request $request   Request object.
         * @param boolean         $creating  True when creating item, false when updating.
         */
        do_action("woocommerce_rest_insert_{$this->post_type}", $post, $request, true);
        $request->set_param('context', 'edit');
        $response = $this->prepare_item_for_response($post, $request);
        $response = rest_ensure_response($response);
        $response->set_status(201);
        $response->header('Location', rest_url(sprintf('/%s/%s/%d', $this->namespace, $this->rest_base, $post_id)));
        return $response;
    }