Breadcrumb Navigation

breadcrumb.navigation.php

<?php
/**
 * Add navigation breadcrumb
 */
 
function wp_nav_breadcrumb( $args = array() ) {
	
	$defaults = array(
		'wrapper' => 'div',
		'wrapper_id' => 'breadcrumbs',
		'wrapper_class' => '',
		'container' => 'nav',
		'container_id' => 'crumbs',
		'container_class' => '',
		'current_before' => '<strong>',
		'current_after' => '</strong>',
		'delimiter' => ' &raquo; ',
		'home_text' => __( 'Home' ),
		'blog_text' => __( 'Blog' ),
		'error404_text' => __( 'Page Not Found' ),
		'search_text' => __( 'Search Results' ),
		'category_archive_text' => __( 'Category Archive' ),
		'tag_archive_text' => __( 'Tag Archive' ),
		'post_format_archive_text' => __( 'Post Format Archive' ),
		'tax_archive_text' => __( 'Taxonomy Archive' ),
		'author_archive_text' => __( 'Posts Published By' ),
		'date_archive_text' => __( 'Posts Published in %s' ),
		'post_type_archive_text' => __( 'Post Type Archive' ),
		'paged_archive_text' => sprintf( __( 'Page %s' ), get_query_var( 'paged' ) ),
		'paged_post_text' => sprintf( __( 'Page %s' ), get_query_var( 'page' ) ),
		'show_category_hierarchy' => true,
		'show_tax_hierarchy' => true,
		'show_page_hierarchy' => true,
		'attachment_tax' => false,
		'single_post_tax' => 'category',
		'single_post_type_tax' => false,
		'output' => 'string',
		'echo' => true
	);
	
	/**
	 * Parse arguments
	 */
	$args = wp_parse_args( $defaults, $args );
	
	/**
	 * Filter arguments
	 */
	$args = apply_filters( 'wp_nav_breadcrumb_args', $args );
	$args = (object) $args;
	
	/**
	 * Early filter override
	 */
	$breadcrumbs = apply_filters( 'pre_wp_nav_breadcrumb', NULL );
	
	if ( NULL !== $breadcrumbs ) {
		if ( $args->echo ) {
			echo $breadcrumbs;
		} else {
			return $breadcrumbs;
		}
	}
	
	/**
	 * Get breadcrumb context
	 */
	$context = wp_nav_breadcrumb_context( $args );

	/**
	 * Construct the breadcrumbs array, with late filter override
	 */
	$breadcrumbs = apply_filters( 'wp_nav_breadcrumb', wp_nav_breadcrumb_construct( $args, $context ) );
	
	
	/**
	 * Output breadcrumb
	 */
	$output = ( 'string' == $args->output ? implode( '', array_values( $breadcrumbs ) : $breadcrumbs );
	
	if ( $args->echo && 'string' == $args->output ) {
		echo $output;
	} else {
		return $output;
	}

}

/**
 * Get breadcrumb context
 */
function wp_nav_breadcrumb_context( $args ) {

	$defaults = array(
		'base_link' => '<a href="' . home_url( '/' ) . '">' . $args->home_text . '</a>',
		'hierarchy' => $args->delimiter,
		'current_location' => '',
		'pagination' => false
	);

	// Base link	
	if ( is_front_page() ) {
		$context = wp_parse_args( 
			$defaults, 
			apply_filters( 'wp_nav_breadcrumb_front_page', array(
				'base_link' => false,
				'hierarchy' => false,
				'current_location' => $defaults->base_link
			) )
		);
	} 
	
	// Define current location for 404 Error page
	elseif ( is_404() ) { 
		$context = wp_parse_args( 
			$defaults, 
			apply_filters( 'wp_nav_breadcrumb_404', array(
				'hierarchy' => false,
				'current_location' => $args->error404_text
			) )
		);
	} 
	
	// Define current location for Search Results page
	elseif ( is_search() ) { 
		$context = wp_parse_args( 
			$defaults, 
			apply_filters( 'wp_nav_breadcrumb_search', array(
				'hierarchy' => $args->search_textt . $args->delimiter,
				'current_location' => get_search_query()
			) )
		);  
	} 
	
	// Define current location for the blog posts index
	elseif ( is_home() ) ) {
		$context = wp_parse_args( 
			$defaults, 
			apply_filters( 'wp_nav_breadcrumb_blog', array(
				'hierarchy' => false,
				'current_location' => ( ! is_paged() ? $args->blog_text : '<a href="' . get_permalink( get_option( 'page_for_posts' ) ) . '">' . $args->blog_text . '</a>' );
			) )
		);
	}
	
	// Define current location for archive pages
	elseif( is_archive() ) {
	
	    // Define Category Hierarchy Crumbs for Category Archive
		if ( is_category() ) { 

			$hierarchy = $args->category_archive_text . $args->delimiter;

			if ( $args->show_category_hierarchy ) {
				global $wp_query;
				$cat_obj = $wp_query->get_queried_object();
				$cat = get_category( $cat_obj->term_id );
				$parentCat = get_category ($cat->parent );
				if ( $cat->parent != 0 ) {
					$hierarchy .= get_category_parents( $parentCat, TRUE, $args->delimiter );
				} 
			}

			$context = wp_parse_args( 
				$defaults, 
				apply_filters( 'wp_nav_breadcrumb_category', array(
					'hierarchy' => $hierarchy,
					'current_location' => single_cat_title( '' , FALSE )
				) )
			);
		} 		
			
		// Define current location for Tag Archives
		elseif ( is_tag() ) {	  
			$context = wp_parse_args( 
				$defaults, 
				apply_filters( 'wp_nav_breadcrumb_tag', array(
					'hierarchy' => $args->tag_archive_text . $args->delimiter,
					'current_location' => single_tag_title( '' , FALSE )
				) )
			);  
		} 
		
		// Define current location for Post Format Archives
		elseif ( is_tax( 'post_format' ) ) { 
			$context = wp_parse_args( 
				$defaults, 
				apply_filters( 'wp_nav_breadcrumb_post_format', array(
					'hierarchy' => $args->post_format_archive_text . $args->delimiter,
					'current_location' => get_post_format_string( get_post_format() )
				) )
			);
		}
		
		// Define current location for Custom Taxonomy Archives
		elseif ( is_tax() ) {

			$hierarchy = $args->tax_archive_text . $args->delimiter;

			if ( $args->show_tax_hierarchy ) {
				global $wp_query;
				$custom_tax = $wp_query->query_vars['taxonomy'];
				$custom_tax_object = get_taxonomy( $custom_tax );
				$post_type_object = get_post_type_object( get_post_type() );
				$custom_tax_link = '<a href="' . get_post_type_archive_link( $post_type_object->name ) . '">' . $post_type_object->labels->name . '</a>';
				$hierarchy = $custom_tax_link . $args->delimiter . $args->tax_archive_text . $args->delimiter;
			}

			$context = wp_parse_args( 
				$defaults, 
				apply_filters( 'wp_nav_breadcrumb_tax', array(
					'hierarchy' => $hierarchy,
					'current_location' => single_term_title( '', false );
				) )
			);
		}
		
		// Define current location for Author Archives
		elseif ( is_author() ) { 
			$context = wp_parse_args( 
				$defaults, 
				apply_filters( 'wp_nav_breadcrumb_author', array(
					'hierarchy' => $args->author_archive_text . $args->delimiter;,
					'current_location' => get_the_author_meta( 'display_name', get_query_var( 'author' ) )
				) )
			);
		} 
	
		// Define Crumbs for Day/Year/Month Date-based Archives
		elseif ( is_date() ) { 

			$year_string = sprintf( 
				'<a href="%1$s">%2$s</a>',
				get_year_link( get_the_time( 'Y' ) ),
				get_the_time( 'Y' )
			);
			$month_string = sprint(
				'<a href="%1$s">%2$s</a>',
				get_month_link( get_the_time( 'Y' ), get_the_time( 'm' ) ),
				get_the_time( 'F' )
			);
				
			// Define Year/Month Hierarchy Crumbs for Day Archive
			if  ( is_day() ) {
				$date_string = $year_string . $args->delimiter . $month_string . $args->delimiter;
				$currentLocation = get_the_time('d'); 
			} 
			// Define Year Hierarchy Crumb for Month Archive
			elseif ( is_month() ) {
				$date_string = $year_string . $args->delimiter;
				$currentLocation = get_the_time( 'F' ); 
			} 
			// Set CurrentLocation for Year Archive
			elseif ( is_year() ) {
				$date_string = '';
				$currentLocation = get_the_time( 'Y' ); 
			}

			$context = wp_parse_args( 
				$defaults, 
				apply_filters( 'wp_nav_breadcrumb_date', array(
					'hierarchy' => sprintf( $args->date_archive_text, $date_string ),
					'current_location' => $currentLocation
				) )
			);
		} 
		
		// Define current location for Custom Post Type Archives
		elseif ( is_post_type_archive( get_post_type() ) ) {

			$post_type_object = get_post_type_object( get_post_type() );

			$context = wp_parse_args( 
				$defaults, 
				apply_filters( 'wp_nav_breadcrumb_post_type_archive', array(
					'hierarchy' => $args->post_type_archive_text . $args->delimiter,
					'current_location' => $post_type_object->labels->name
				) )
			);
		}		
 
		// Define pagination for paged Archive pages
		if ( get_query_var( 'paged' ) ) {
			$context['pagination'] = $args->delimiter . $args->paged_archive_text;
		}
	
	}
	
	// Define current location for singular pages
	elseif ( is_singular() ) {
	
		if ( is_page() & ! is_front_page() ) {
			$context = wp_parse_args( 
				$defaults, 
				apply_filters( 'wp_nav_breadcrumb_page', array(
					'hierarchy' => ( $args->show_page_hierarchy ? wp_nav_breadcrumb_page_hierarchy( $args->delimiter ) : false ),
					'current_location' => get_the_title()
				) )
			);
		}
	
		// Define Category and Parent Post Crumbs for Post Attachments
		elseif ( is_attachment() ) { 

			if ( $args->attachment_tax ) {
				if ( 'category' == $args->attachment_tax ) {
					$hierarchy = wp_nav_breadcrumb_cat_hierarchy( $args->delimiter );
				} else if ( 'post_tag' == $args->attachment_tax ) {
					$hierarchy = wp_nav_breadcrumb_tag_hierarchy( $args->delimiter );
				} else if ( 'post_format' == $args->attachment_tax ) {
					$hierarchy = wp_nav_breadcrumb_post_format_hierarchy( $args->delimiter );
				} else {
					$hierarchy = wp_nav_breadcrumb_tax_hierarchy( $args->attachment_tax, $args->delimiter );
				}
			} 
			// Get parent post
			global $post;
			$parent = get_post( $post->post_parent );
			$hierarchy .= '<a href="' . get_permalink ( $parent->ID ) . '">' . $parent->post_title . '</a> ' . $args->delimiter;

			$context = wp_parse_args( 
				$defaults, 
				apply_filters( 'wp_nav_breadcrumb_attachment', array(
					'hierarchy' => $hierarchy,
					'current_location' => get_the_title()
				) )
			);
		}
		
		// Define Category Hierarchy Crumbs for Single Posts
		elseif ( is_singular( 'post' ) ) { 

			if ( $args->single_post_tax ) {
				if ( 'category' == $args->single_post_tax ) {
					$hierarchy = wp_nav_breadcrumb_cat_hierarchy( $args->delimiter );
				} else if ( 'post_tag' == $args->single_post_tax ) {
					$hierarchy = wp_nav_breadcrumb_tag_hierarchy( $args->delimiter );
				} else if ( 'post_format' == $args->single_post_tax ) {
					$hierarchy = wp_nav_breadcrumb_post_format_hierarchy( $args->delimiter );
				} else {
					$hierarchy = wp_nav_breadcrumb_tax_hierarchy( $args->single_post_tax, $args->delimiter );
				}
			}

			$context = wp_parse_args( 
				$defaults, 
				apply_filters( 'wp_nav_breadcrumb_single_blog_post', array(
					'hierarchy' => $hierarchy,
					'current_location' => get_the_title()
				) )
			);
		}
		
		// Define current location for Custom Post Types
		elseif ( is_singular( get_post_type() ) ) {
			
			$post_type_object = get_post_type_object( get_post_type() );
			
			$hierarchy .= '<a href="' . get_post_type_archive_link( $post_type_object->name ) . '">' . $post_type_object->labels->name . '</a>' . $args->delimiter;
	
			if ( $args->single_post_type_tax ) {
				global $post;
				if ( $args->single_post_type_tax && in_array( $post->post_type, get_object_taxonomies( $post->post_type, $args->single_post_type_tax ) ) ) {
					$hierarchy .= wp_nav_breadcrumb_tax_hierarchy( $args->single_post_type_tax, $args->delimiter );
				} else {
					$taxonomies = get_object_taxonomies( get_post_type() );
					$tax = ( ! empty( $taxonomies ) ? $taxonomies[0] : false );
					if ( $tax ) {
						$hierarchy .= wp_nav_breadcrumb_tax_hierarchy( $tax, $args->delimiter );
					}
				}
			}	

			$context = wp_parse_args( 
				$defaults, 
				apply_filters( 'wp_nav_breadcrumb_single_post_type', array(
					'hierarchy' => $hierarchy,
					'current_location' => get_the_title()
				) )
			);
		}
 
		// Define pagination for singular pages
		if ( get_query_var( 'page' ) ) {
			$context['pagination'] = $args->delimiter . $args->paged_post_text;
		}
	
	}
	// Return $context
	return ( isset( $context ) ? $context : $defaults );
}

/**
 * Breadcrumb construct
 */
function wp_nav_breadcrumb_construct( $args, $context ) {

	$breadcrumbs = array();

	// Opening wrapper
	$wrapper_id = ( $args->wrapper_id ? ' id="' . esc_attr( $args->wrapper_id ) . '"';
	$wrapper_class = ( $args->wrapper_class ? ' class="' . esc_attr( $args->wrapper_class ) . '"';
	$breadcrumbs['wrapper_open'] = '<' . $args->wrapper . $wrapper_id . $wrapper_class . '>';
	
	// Opening container
	$container_id = ( $args->container_id ? ' id="' . esc_attr( $args->container_id ) . '"';
	$container_class = ( $args->container_class ? ' class="' . esc_attr( $args->container_class ) . '"';
	$breadcrumbs['container_open'] = '<' . $args->container . $container_id . $container_class . '>';
	
	// Base link
	if ( $context['base_link'] ) {
		$breadcrumbs['base_link'] = $context['base_link'];
	}
	
	// Contextual hierarchy
	$breadcrumbs['hierarchy'] = $context['hierarchy'];
	
	// Opening element that wraps the current page breadcrumb link
	$breadcrumbs['current_before'] = $args->current_before;
	// Current location
	$breadcrumbs['current_location'] = $context['current_location'];
	//Closing element that wraps the current page breadcrumb link
	$breadcrumbs['current_after'] = $args->current_after;
	
	// Pagination
	if ( $context['pagination'] ) {
		$breadcrumbs['pagination'] = $context['pagination'];
	}
	
	// Closing element that wraps entire breadcrumb output
	$breadcrumbs['container_close'] = '</' . $args->container . '>';
	// Closing breadcrumb element
	$breadcrumbs['wrapper_close'] = '</' . $args->wrapper . '>';

	// Return $breadcrumbs
	return $breadcrumbs;
}


/**
 * Page hierarchy
 */
function wp_nav_breadcrumb_page_hierarchy( $delimiter ) {
	global $post;
	if ( ! $post->post_parent ) {
		return false;
	} else {
		$hierarchy = false;
		$parent_id  = $post->post_parent;
		$pagecrumbs = array();
		while ( $parent_id ) {
			$page = get_page( $parent_id );
			$pagecrumbs[] = '<a href="' . get_permalink( $page->ID ) . '">' . get_the_title( $page->ID ) . '</a>';
			$parent_id  = $page->post_parent;
		}
		$pagecrumbs = array_reverse( $pagecrumbs );
		foreach ( $pagecrumbs as $crumb ) {
			$hierarchy .= $crumb . $delimiter;
		}
		return $hierarchy;
	}
}

/**
 * Category hierarchy
 */
function wp_nav_breadcrumb_cat_hierarchy( $delimiter ) {
	global $post;
	// Ensure post type supports 'category' taxonomy
	if ( ! in_array( $post->post_type, get_object_taxonomies( $post->post_type, 'category' ) ) ) {
		return false;
	} else {
		$hierarchy = false;
		$cats = get_the_category(); 
		$cat = ( ! empty( $cats ) ? $cats[0] : false );
		// Determine if category is hierarchical
		if ( $cat ) {
			$hierarchy .= get_category_parents( $cat->ID, TRUE, $delimiter );
		}
		return $hierarchy;
	} 
}

/**
 * Tag hierarchy
 */
function wp_nav_breadcrumb_tag_hierarchy( $delimiter ) {
	global $post;
	// Ensure post type supports 'post_tag' taxonomy
	if ( ! in_array( $post->post_type, get_object_taxonomies( $post->post_type, 'post_tag' ) ) ) {
		return false;
	} else {
		$tags = get_the_tags( $post->ID );
		if ( ! $tags ) {
			return false;
		}
		return '<a href="' . get_tag_link( $tags[0]->ID ) . '">' . $tags[0]->name . '</a>' . $delimiter;
	}
}

/**
 * Post Format hierarchy
 */
function wp_nav_breadcrumb_post_format_hierarchy( $delimiter ) {
	global $post;
	// Ensure post type supports 'post_tag' taxonomy
	if ( ! in_array( $post->post_type, get_object_taxonomies( $post->post_type, 'post_format' ) ) || ! get_post_format( $post->ID ) ) {
		return false;
	} else {
		$post_format = get_post_format( $post->ID );
		return '<a href="' . get_post_format_link( $post_format ) . '">' . get_post_format_string( $post_format ) . '</a>' . $delimiter;
	}
}

/**
 * Tax hierarchy
 */
function wp_nav_breadcrumb_tax_hierarchy( $tax, $delimiter ) {
	global $post;
	// Ensure post type supports 'category' taxonomy
	if ( ! in_array( $post->post_type, get_object_taxonomies( $post->post_type, $tax ) ) ) {
		return false;
	} else {
		$hierarchy = false;
		$terms = get_the_terms( $post->ID, $tax );
		if ( ! $terms ) {
			return false;
		}		
		if ( $terms[0]->parent ) {
			// Get term hierarchy
			$parent_id  = $terms[0]->parent;
			$term_crumbs = array();
			while ( $parent_id ) {
				$crumb = get_term_by( 'id', $parent_id, $tax );
				$term_crumbs[] = '<a href="' . get_term_link( $crumb->term_id ) . '">' . $crumb->name . '</a>';
				$parent_id  = $crumb->parent;
			}
			$term_crumbs = array_reverse( $term_crumbs );
			foreach ( $term_crumbs as $crumb ) {
				$hierarchy .= $crumb . $delimiter;
			}
		}
		$hierarchy .= '<a href="' . get_term_link( $terms[0]->ID ) . '">' . $terms[0]->name . '</a>' . $delimiter;
		return $hierarchy;
	} 
}

Broke out contextual breadcrumbs into subordinate functions. H/T @Kaiser

Added args array and defaults, in preparation of making args array filterable, and refactoring.