class-json-ld-breadcrumbs.php

<?php
/**
 * Class JSON LD Breadcrumb.
 *
 * @package  JSON_LD_Breadcrumbs
 */

// Exit if the file is called directy by URL.
defined( 'ABSPATH' ) || exit;

if ( ! class_exists( 'JSON_LD_Breadcrumbs' ) ) {

	/**
	 * Class JSON LD Breadcrumb.
	 *
	 * @since  1.0.0
	 */
	class JSON_LD_Breadcrumbs {

		/**
		 * Instance of JSON_LD_Breadcrumbs
		 *
		 * @since  v1.0.0
		 * @var Object JSON_LD_Breadcrumbs
		 */
		private static $instance = null;

		/**
		 * Crumb position. Increases everytime a new crumb is added.
		 *
		 * @since  1.0.0
		 * @var integer
		 */
		private $crumb_position = 0;

		/**
		 * Crunbs Array
		 *
		 * @since  1.0.0
		 * @var array
		 */
		private $crumbs = array();

		/**
		 * Initiate the class JSON_LD_Breadcrumbs
		 *
		 * @since  1.0.0
		 * @return (Object) Instance of JSON_LD_Breadcrumbs
		 */
		public static function instance() {
			if ( ! isset( self::$instance ) ) {
				self::$instance = new self();
			}

			return self::$instance;
		}

		/**
		 * Constructor.
		 *
		 * @since  1.0.0
		 */
		private function __construct() {
			$this->post           = ( isset( $GLOBALS['post'] ) ? $GLOBALS['post'] : null );
			$this->show_on_front  = get_option( 'show_on_front' );
			$this->page_for_posts = get_option( 'page_for_posts' );

			add_action( 'wp_head', array( $this, 'set_crumbs' ) );
		}

		/**
		 * Initialize the Schema for the breadcrumbs markup.
		 *
		 * @since  1.0.0
		 *
		 * @param  (Array) $breadcrumb Breadcrumbs array.
		 *
		 * @return (Array) $breadcrumb Breadcrumbs array.
		 */
		private function initialize_breadcrumb_schema( $breadcrumb ) {
			$breadcrumb['@context'] = 'http://schema.org';
			$breadcrumb['@type']    = 'BreadcrumbList';

			return $breadcrumb;
		}

		/**
		 * Adds homepage to the breadcrumb.
		 *
		 * @since  1.0.0
		 */
		private function maybe_add_home_crumb() {
			// TODO: Add option in the admin panel to enable or disable home page in breadcrumb.
			// TODO: Add option in the admin panel to choose the text for home page.
			$this->add_crumb(
				'Home',
				get_site_url()
			);
		}

		/**
		 * Conditionally adds blog page to the breadcrumb.
		 *
		 * @since  1.0.0
		 */
		private function maybe_add_blog_crumb() {
			if ( ( 'page' === $this->show_on_front && 'post' === get_post_type() ) && ( ! is_home() && ! is_search() ) ) {
				if ( $this->page_for_posts ) {
					$this->add_crumb( get_the_title( $this->page_for_posts ), get_permalink( $this->page_for_posts ) );
				}
			}
		}

		/**
		 * Add crumb to the breadcrumbs array.
		 *
		 * @since  1.0.0
		 *
		 * @param String $name Name of the Breadcrumb element.
		 * @param string $url URL of the Breadcrumb element.
		 * @param string $image Image URL of the Breadcrumb element.
		 */
		private function add_crumb( $name, $url = '', $image = '' ) {
			$this->crumb_position = $this->crumb_position + 1;

			if ( '' === $image ) {
				$this->crumbs[] = array(
					'@type'    => 'ListItem',
					'position' => $this->crumb_position,
					'item'     => array(
						'@id'  => $url,
						'name' => $name,
					),
				);
			} else {
				$this->crumbs[] = array(
					'@type'    => 'ListItem',
					'position' => $this->crumb_position,
					'item'     => array(
						'@id'   => $url,
						'name'  => $name,
						'image' => $image,
					),
				);
			}
		}

		/**
		 * Post type archive title.
		 *
		 * @since  1.0.0
		 *
		 * @param  string $pt The name of a registered post type.
		 *
		 * @return String     Title of the post type.
		 */
		private function post_type_archive_title( $pt ) {
			$archive_title = '';

			$post_type_obj = get_post_type_object( $pt );
			if ( is_object( $post_type_obj ) ) {
				if ( isset( $post_type_obj->label ) && '' !== $post_type_obj->label ) {
					$archive_title = $post_type_obj->label;
				} elseif ( isset( $post_type_obj->labels->menu_name ) && '' !== $post_type_obj->labels->menu_name ) {
					$archive_title = $post_type_obj->labels->menu_name;
				} else {
					$archive_title = $post_type_obj->name;
				}
			}

			return $archive_title;
		}

		/**
		 * Conditionally adds the post type archive to the breadcrumb.
		 *
		 * @since  1.0.0
		 */
		private function maybe_add_pt_archive_crumb_for_post() {
			if ( 'post' === $this->post->post_type ) {
				return;
			}
			if ( isset( $this->post->post_type ) && get_post_type_archive_link( $this->post->post_type ) ) {
				$this->add_crumb( $this->post_type_archive_title( $this->post->post_type ), get_post_type_archive_link( $this->post->post_type ) );
			}
		}

		/**
		 * Conditionally adds taxanomy titles to the breadcrumb.
		 *
		 * @since  1.0.0
		 */
		private function maybe_add_taxonomy_crumbs_for_post() {
			// TODO: Add an option in admin panel to choose taxanomy base in the breadcrumb.
		}

		/**
		 * Adds post ancestor to the breadcrumb.
		 *
		 * @since  1.0.0
		 */
		private function add_post_ancestor_crumbs() {
			$ancestors = $this->get_post_ancestors();
			if ( is_array( $ancestors ) && array() !== $ancestors ) {
				foreach ( $ancestors as $ancestor ) {
					$this->add_crumb( get_the_title( $ancestor ), get_permalink( $ancestor ) );
				}
			}
		}

		/**
		 * Finds the post ancestors.
		 *
		 * @since  1.0.0
		 * @return Array Ancestors for the current page.
		 */
		private function get_post_ancestors() {
			$ancestors = array();

			if ( isset( $this->post->ancestors ) ) {
				if ( is_array( $this->post->ancestors ) ) {
					$ancestors = array_values( $this->post->ancestors );
				} else {
					$ancestors = array( $this->post->ancestors );
				}
			} elseif ( isset( $this->post->post_parent ) ) {
				$ancestors = array( $this->post->post_parent );
			}

			// Reverse the order so it's oldest to newest.
			$ancestors = array_reverse( $ancestors );

			return $ancestors;
		}

		/**
		 * Add Taxanomies to breadcrumb.
		 *
		 * @since  1.0.0
		 */
		private function add_crumbs_for_taxonomy() {
			$term = $GLOBALS['wp_query']->get_queried_object();
			$this->add_crumb( $term->name, get_term_link( $term ) );
		}

		/**
		 * Add month to the breadcrumb.
		 *
		 * @since  1.0.0
		 */
		private function add_month_crumb() {
			$this->add_crumb(
				'Archives for ' . esc_html( single_month_title( ' ', false ) ),
				get_month_link( get_query_var( 'y' ), get_query_var( 'monthnum' ) )
			);
		}

		/**
		 * Add Month and year to breadcrumb for date archive.
		 *
		 * @since  1.0.0
		 */
		private function add_linked_month_year_crumb() {
			$this->add_crumb(
				$GLOBALS['wp_locale']->get_month( get_query_var( 'monthnum' ) ) . ' ' . get_query_var( 'year' ),
				get_month_link( get_query_var( 'year' ), get_query_var( 'monthnum' ) )
			);
		}

		/**
		 * Add date to the breadcrumb.
		 *
		 * @since  1.0.0
		 */
		private function add_date_crumb() {
			$this->add_crumb(
				'Archives for ' . esc_html( single_month_title( ' ', false ) ),
				get_day_link( get_query_var( 'year' ), get_query_var( 'monthnum' ), get_query_var( 'day' ) )
			);
		}

		/**
		 * Add year to the breadcrumb.
		 *
		 * @since  1.0.0
		 */
		private function add_year_crumb() {
			$this->add_crumb(
				'Archives for ' . esc_html( get_query_var( 'year' ) ),
				get_year_link( get_query_var( 'year' ) )
			);
		}

		/**
		 * Conditionally add individual crumbs to the breadcrumb.
		 *
		 * @since  1.0.0
		 */
		private function add_breadcrumb_crumbs() {
			global $wp_query;

			$this->maybe_add_home_crumb();
			$this->maybe_add_blog_crumb();

			if ( ( 'page' === $this->show_on_front && is_front_page() ) || ( 'posts' === $this->show_on_front && is_home() ) ) { // phpcs:ignore Generic.CodeAnalysis.EmptyStatement.DetectedIf
				// Do nothing.
			} elseif ( 'page' === $this->show_on_front && is_home() ) {
				$this->add_crumb( get_the_title( $this->page_for_posts ), get_permalink( $this->page_for_posts ) );
			} elseif ( is_singular() ) {
				$this->maybe_add_pt_archive_crumb_for_post();

				if ( isset( $this->post->post_parent ) && 0 === $this->post->post_parent ) {
					$this->maybe_add_taxonomy_crumbs_for_post();
				} else {
					$this->add_post_ancestor_crumbs();
				}

				if ( isset( $this->post->ID ) ) {
					$this->add_crumb( get_the_title( $this->post->ID ), get_permalink( $this->post->ID ) );
				}
			} else {
				if ( is_post_type_archive() ) {
					$post_type = $wp_query->get( 'post_type' );

					if ( $post_type && is_string( $post_type ) ) {
						$this->add_crumb( $this->post_type_archive_title( $post_type ), get_post_type_archive_link( $post_type ) );
					}
				} elseif ( is_tax() || is_tag() || is_category() ) {
					$this->add_crumbs_for_taxonomy();
				} elseif ( is_date() ) {
					if ( is_day() ) {
						$this->add_linked_month_year_crumb();
						$this->add_date_crumb();
					} elseif ( is_month() ) {
						$this->add_month_crumb();
					} elseif ( is_year() ) {
						$this->add_year_crumb();
					}
				} elseif ( is_author() ) {
					$user = $wp_query->get_queried_object();
					$this->add_crumb(
						'Archives for ' . $user->display_name,
						get_author_posts_url( $user->ID, $user->nicename )
					);
				} elseif ( is_search() ) {
					$this->add_crumb(
						'Search results for ' . esc_html( get_search_query() ),
						get_search_link( get_query_var( 's' ) )
					);
				} elseif ( is_404() ) {
					$this->add_crumb(
						'Error 404: Page not found',
						null
					);
				}
			}

			return apply_filters( 'json_ld_breadcrumb_itemlist_array', $this->crumbs );
		}

		/**
		 * Initialize the breadcrumbs.
		 *
		 * @since  1.0.0
		 */
		public function set_crumbs() {
			$breadcrumb = array();
			$breadcrumb = $this->initialize_breadcrumb_schema( $breadcrumb );

			$breadcrumb['itemListElement'] = $this->add_breadcrumb_crumbs();

			$this->json_schema( apply_filters( 'json_ld_breadcrumb_array', $breadcrumb ) );
		}

		/**
		 * Output the ld+json schema markup.
		 *
		 * @since  1.0.0
		 *
		 * @param  Array $schema Array to be converted to json markup.
		 */
		private function json_schema( $schema ) {
			$schema_output = null;

			if ( ! empty( $schema ) && is_array( $schema ) ) {
				$schema_output .= '<script type="application/ld+json">' . wp_json_encode( $schema, JSON_PRETTY_PRINT | JSON_UNESCAPED_SLASHES ) . '</script>';
			}

			echo $schema_output; // phpcs:ignore WordPress.Security.EscapeOutput.OutputNotEscaped
		}

	}

}