WP_REST_Posts_Controller::get_items() WordPress Method

	public function get_items( $request ) {

		// Ensure a search string is set in case the orderby is set to 'relevance'.
		if ( ! empty( $request['orderby'] ) && 'relevance' === $request['orderby'] && empty( $request['search'] ) ) {
			return new WP_Error(
				'rest_no_search_term_defined',
				__( 'You need to define a search term to order by relevance.' ),
				array( 'status' => 400 )
			);
		}

		// Ensure an include parameter is set in case the orderby is set to 'include'.
		if ( ! empty( $request['orderby'] ) && 'include' === $request['orderby'] && empty( $request['include'] ) ) {
			return new WP_Error(
				'rest_orderby_include_missing_include',
				__( 'You need to define an include parameter to order by include.' ),
				array( 'status' => 400 )
			);
		}

		// Retrieve the list of registered collection query parameters.
		$registered = $this->get_collection_params();
		$args       = array();

		/*
		 * This array defines mappings between public API query parameters whose
		 * values are accepted as-passed, and their internal WP_Query parameter
		 * name equivalents (some are the same). Only values which are also
		 * present in $registered will be set.
		 */
		$parameter_mappings = array(
			'author'         => 'author__in',
			'author_exclude' => 'author__not_in',
			'exclude'        => 'post__not_in',
			'include'        => 'post__in',
			'menu_order'     => 'menu_order',
			'offset'         => 'offset',
			'order'          => 'order',
			'orderby'        => 'orderby',
			'page'           => 'paged',
			'parent'         => 'post_parent__in',
			'parent_exclude' => 'post_parent__not_in',
			'search'         => 's',
			'slug'           => 'post_name__in',
			'status'         => 'post_status',
		);

		/*
		 * For each known parameter which is both registered and present in the request,
		 * set the parameter's value on the query $args.
		 */
		foreach ( $parameter_mappings as $api_param => $wp_param ) {
			if ( isset( $registered[ $api_param ], $request[ $api_param ] ) ) {
				$args[ $wp_param ] = $request[ $api_param ];
			}
		}

		// Check for & assign any parameters which require special handling or setting.
		$args['date_query'] = array();

		if ( isset( $registered['before'], $request['before'] ) ) {
			$args['date_query'][] = array(
				'before' => $request['before'],
				'column' => 'post_date',
			);
		}

		if ( isset( $registered['modified_before'], $request['modified_before'] ) ) {
			$args['date_query'][] = array(
				'before' => $request['modified_before'],
				'column' => 'post_modified',
			);
		}

		if ( isset( $registered['after'], $request['after'] ) ) {
			$args['date_query'][] = array(
				'after'  => $request['after'],
				'column' => 'post_date',
			);
		}

		if ( isset( $registered['modified_after'], $request['modified_after'] ) ) {
			$args['date_query'][] = array(
				'after'  => $request['modified_after'],
				'column' => 'post_modified',
			);
		}

		// Ensure our per_page parameter overrides any provided posts_per_page filter.
		if ( isset( $registered['per_page'] ) ) {
			$args['posts_per_page'] = $request['per_page'];
		}

		if ( isset( $registered['sticky'], $request['sticky'] ) ) {
			$sticky_posts = get_option( 'sticky_posts', array() );
			if ( ! is_array( $sticky_posts ) ) {
				$sticky_posts = array();
			}
			if ( $request['sticky'] ) {
				/*
				 * As post__in will be used to only get sticky posts,
				 * we have to support the case where post__in was already
				 * specified.
				 */
				$args['post__in'] = $args['post__in'] ? array_intersect( $sticky_posts, $args['post__in'] ) : $sticky_posts;

				/*
				 * If we intersected, but there are no post IDs in common,
				 * WP_Query won't return "no posts" for post__in = array()
				 * so we have to fake it a bit.
				 */
				if ( ! $args['post__in'] ) {
					$args['post__in'] = array( 0 );
				}
			} elseif ( $sticky_posts ) {
				/*
				 * As post___not_in will be used to only get posts that
				 * are not sticky, we have to support the case where post__not_in
				 * was already specified.
				 */
				$args['post__not_in'] = array_merge( $args['post__not_in'], $sticky_posts );
			}
		}

		$args = $this->prepare_tax_query( $args, $request );

		// Force the post_type argument, since it's not a user input variable.
		$args['post_type'] = $this->post_type;

		/**
		 * Filters WP_Query arguments when querying posts via the REST API.
		 *
		 * The dynamic portion of the hook name, `$this->post_type`, refers to the post type slug.
		 *
		 * Possible hook names include:
		 *
		 *  - `rest_post_query`
		 *  - `rest_page_query`
		 *  - `rest_attachment_query`
		 *
		 * Enables adding extra arguments or setting defaults for a post collection request.
		 *
		 * @since 4.7.0
		 * @since 5.7.0 Moved after the `tax_query` query arg is generated.
		 *
		 * @link /reference/classes/wp_query/
		 *
		 * @param array           $args    Array of arguments for WP_Query.
		 * @param WP_REST_Request $request The REST API request.
		 */
		$args       = apply_filters( "rest_{$this->post_type}_query", $args, $request );
		$query_args = $this->prepare_items_query( $args, $request );

		$posts_query  = new WP_Query();
		$query_result = $posts_query->query( $query_args );

		// Allow access to all password protected posts if the context is edit.
		if ( 'edit' === $request['context'] ) {
			add_filter( 'post_password_required', array( $this, 'check_password_required' ), 10, 2 );
		}

		$posts = array();

		foreach ( $query_result as $post ) {
			if ( ! $this->check_read_permission( $post ) ) {
				continue;
			}

			$data    = $this->prepare_item_for_response( $post, $request );
			$posts[] = $this->prepare_response_for_collection( $data );
		}

		// Reset filter.
		if ( 'edit' === $request['context'] ) {
			remove_filter( 'post_password_required', array( $this, 'check_password_required' ) );
		}

		$page        = (int) $query_args['paged'];
		$total_posts = $posts_query->found_posts;

		if ( $total_posts < 1 ) {
			// Out-of-bounds, run the query again without LIMIT for total count.
			unset( $query_args['paged'] );

			$count_query = new WP_Query();
			$count_query->query( $query_args );
			$total_posts = $count_query->found_posts;
		}

		$max_pages = ceil( $total_posts / (int) $posts_query->query_vars['posts_per_page'] );

		if ( $page > $max_pages && $total_posts > 0 ) {
			return new WP_Error(
				'rest_post_invalid_page_number',
				__( 'The page number requested is larger than the number of pages available.' ),
				array( 'status' => 400 )
			);
		}

		$response = rest_ensure_response( $posts );

		$response->header( 'X-WP-Total', (int) $total_posts );
		$response->header( 'X-WP-TotalPages', (int) $max_pages );

		$request_params = $request->get_query_params();
		$base           = add_query_arg( urlencode_deep( $request_params ), rest_url( sprintf( '%s/%s', $this->namespace, $this->rest_base ) ) );

		if ( $page > 1 ) {
			$prev_page = $page - 1;

			if ( $prev_page > $max_pages ) {
				$prev_page = $max_pages;
			}

			$prev_link = add_query_arg( 'page', $prev_page, $base );
			$response->link_header( 'prev', $prev_link );
		}
		if ( $max_pages > $page ) {
			$next_page = $page + 1;
			$next_link = add_query_arg( 'page', $next_page, $base );

			$response->link_header( 'next', $next_link );
		}

		return $response;
	}