Source

File: wp-includes/rest-api/endpoints/class-wp-rest-posts-controller.php

protected function prepare_item_for_database( $request ) {
		$prepared_post = new stdClass();

		// Post ID.
		if ( isset( $request['id'] ) ) {
			$existing_post = $this->get_post( $request['id'] );
			if ( is_wp_error( $existing_post ) ) {
				return $existing_post;
			}

			$prepared_post->ID = $existing_post->ID;
		}

		$schema = $this->get_item_schema();

		// Post title.
		if ( ! empty( $schema['properties']['title'] ) && isset( $request['title'] ) ) {
			if ( is_string( $request['title'] ) ) {
				$prepared_post->post_title = $request['title'];
			} elseif ( ! empty( $request['title']['raw'] ) ) {
				$prepared_post->post_title = $request['title']['raw'];
			}
		}

		// Post content.
		if ( ! empty( $schema['properties']['content'] ) && isset( $request['content'] ) ) {
			if ( is_string( $request['content'] ) ) {
				$prepared_post->post_content = $request['content'];
			} elseif ( isset( $request['content']['raw'] ) ) {
				$prepared_post->post_content = $request['content']['raw'];
			}
		}

		// Post excerpt.
		if ( ! empty( $schema['properties']['excerpt'] ) && isset( $request['excerpt'] ) ) {
			if ( is_string( $request['excerpt'] ) ) {
				$prepared_post->post_excerpt = $request['excerpt'];
			} elseif ( isset( $request['excerpt']['raw'] ) ) {
				$prepared_post->post_excerpt = $request['excerpt']['raw'];
			}
		}

		// Post type.
		if ( empty( $request['id'] ) ) {
			// Creating new post, use default type for the controller.
			$prepared_post->post_type = $this->post_type;
		} else {
			// Updating a post, use previous type.
			$prepared_post->post_type = get_post_type( $request['id'] );
		}

		$post_type = get_post_type_object( $prepared_post->post_type );

		// Post status.
		if ( ! empty( $schema['properties']['status'] ) && isset( $request['status'] ) ) {
			$status = $this->handle_status_param( $request['status'], $post_type );

			if ( is_wp_error( $status ) ) {
				return $status;
			}

			$prepared_post->post_status = $status;
		}

		// Post date.
		if ( ! empty( $schema['properties']['date'] ) && ! empty( $request['date'] ) ) {
			$current_date = isset( $prepared_post->ID ) ? get_post( $prepared_post->ID )->post_date : false;
			$date_data    = rest_get_date_with_gmt( $request['date'] );

			if ( ! empty( $date_data ) && $current_date !== $date_data[0] ) {
				list( $prepared_post->post_date, $prepared_post->post_date_gmt ) = $date_data;
				$prepared_post->edit_date                                        = true;
			}
		} elseif ( ! empty( $schema['properties']['date_gmt'] ) && ! empty( $request['date_gmt'] ) ) {
			$current_date = isset( $prepared_post->ID ) ? get_post( $prepared_post->ID )->post_date_gmt : false;
			$date_data    = rest_get_date_with_gmt( $request['date_gmt'], true );

			if ( ! empty( $date_data ) && $current_date !== $date_data[1] ) {
				list( $prepared_post->post_date, $prepared_post->post_date_gmt ) = $date_data;
				$prepared_post->edit_date                                        = true;
			}
		}

		// Sending a null date or date_gmt value resets date and date_gmt to their
		// default values (`0000-00-00 00:00:00`).
		if (
			( ! empty( $schema['properties']['date_gmt'] ) && $request->has_param( 'date_gmt' ) && null === $request['date_gmt'] ) ||
			( ! empty( $schema['properties']['date'] ) && $request->has_param( 'date' ) && null === $request['date'] )
		) {
			$prepared_post->post_date_gmt = null;
			$prepared_post->post_date     = null;
		}

		// Post slug.
		if ( ! empty( $schema['properties']['slug'] ) && isset( $request['slug'] ) ) {
			$prepared_post->post_name = $request['slug'];
		}

		// Author.
		if ( ! empty( $schema['properties']['author'] ) && ! empty( $request['author'] ) ) {
			$post_author = (int) $request['author'];

			if ( get_current_user_id() !== $post_author ) {
				$user_obj = get_userdata( $post_author );

				if ( ! $user_obj ) {
					return new WP_Error(
						'rest_invalid_author',
						__( 'Invalid author ID.' ),
						array( 'status' => 400 )
					);
				}
			}

			$prepared_post->post_author = $post_author;
		}

		// Post password.
		if ( ! empty( $schema['properties']['password'] ) && isset( $request['password'] ) ) {
			$prepared_post->post_password = $request['password'];

			if ( '' !== $request['password'] ) {
				if ( ! empty( $schema['properties']['sticky'] ) && ! empty( $request['sticky'] ) ) {
					return new WP_Error(
						'rest_invalid_field',
						__( 'A post can not be sticky and have a password.' ),
						array( 'status' => 400 )
					);
				}

				if ( ! empty( $prepared_post->ID ) && is_sticky( $prepared_post->ID ) ) {
					return new WP_Error(
						'rest_invalid_field',
						__( 'A sticky post can not be password protected.' ),
						array( 'status' => 400 )
					);
				}
			}
		}

		if ( ! empty( $schema['properties']['sticky'] ) && ! empty( $request['sticky'] ) ) {
			if ( ! empty( $prepared_post->ID ) && post_password_required( $prepared_post->ID ) ) {
				return new WP_Error(
					'rest_invalid_field',
					__( 'A password protected post can not be set to sticky.' ),
					array( 'status' => 400 )
				);
			}
		}

		// Parent.
		if ( ! empty( $schema['properties']['parent'] ) && isset( $request['parent'] ) ) {
			if ( 0 === (int) $request['parent'] ) {
				$prepared_post->post_parent = 0;
			} else {
				$parent = get_post( (int) $request['parent'] );

				if ( empty( $parent ) ) {
					return new WP_Error(
						'rest_post_invalid_id',
						__( 'Invalid post parent ID.' ),
						array( 'status' => 400 )
					);
				}

				$prepared_post->post_parent = (int) $parent->ID;
			}
		}

		// Menu order.
		if ( ! empty( $schema['properties']['menu_order'] ) && isset( $request['menu_order'] ) ) {
			$prepared_post->menu_order = (int) $request['menu_order'];
		}

		// Comment status.
		if ( ! empty( $schema['properties']['comment_status'] ) && ! empty( $request['comment_status'] ) ) {
			$prepared_post->comment_status = $request['comment_status'];
		}

		// Ping status.
		if ( ! empty( $schema['properties']['ping_status'] ) && ! empty( $request['ping_status'] ) ) {
			$prepared_post->ping_status = $request['ping_status'];
		}

		if ( ! empty( $schema['properties']['template'] ) ) {
			// Force template to null so that it can be handled exclusively by the REST controller.
			$prepared_post->page_template = null;
		}

		/**
		 * Filters a post before it is inserted via the REST API.
		 *
		 * The dynamic portion of the hook name, `$this->post_type`, refers to the post type slug.
		 *
		 * @since 4.7.0
		 *
		 * @param stdClass        $prepared_post An object representing a single post prepared
		 *                                       for inserting or updating the database.
		 * @param WP_REST_Request $request       Request object.
		 */
		return apply_filters( "rest_pre_insert_{$this->post_type}", $prepared_post, $request );

	}