bootstrap-breadcrumb.php

<?php

/**
 * Retrieve category parents.
 *
 * @param int $id Category ID.
 * @param array $visited Optional. Already linked to categories to prevent duplicates.
 * @return string|WP_Error A list of category parents on success, WP_Error on failure.
 */
function custom_get_category_parents( $id, $visited = array() ) {
  $chain = '';
  $parent = get_term( $id, 'category' );
  
  if ( is_wp_error( $parent ) )
    return $parent;
  
  $name = $parent->name;
  
  if ( $parent->parent && ( $parent->parent != $parent->term_id ) && !in_array( $parent->parent, $visited ) ) {
    $visited[] = $parent->parent;
    $chain .= custom_get_category_parents( $parent->parent, $visited );
  }
  
  $chain .= '<li class="breadcrumb-item"><a href="' . esc_url( get_category_link( $parent->term_id ) ) . '">' . $name. '</a>' . '</li>';
  
  return $chain;
}


function bootstrap_breadcrumb() {
  global $post;
  
  $html = '<ol class="breadcrumb">';
  
  if ( (is_front_page()) || (is_home()) ) {
    $html .= '<li class="breadcrumb-item active">Home</li>';
  }
  
  else {
    $html .= '<li class="breadcrumb-item"><a href="'.esc_url(home_url('/')).'">Home</a></li>';
    
    if ( is_attachment() ) {
      $parent = get_post($post->post_parent);
      $categories = get_the_category($parent->ID);
      
      if ( $categories[0] ) {
        $html .= custom_get_category_parents($categories[0]);
      }
      
      $html .= '<li class="breadcrumb-item"><a href="' . esc_url( get_permalink( $parent ) ) . '">' . $parent->post_title . '</a></li>';
      $html .= '<li class="breadcrumb-item active">' . get_the_title() . '</li>';
    }
    
    elseif ( is_category() ) {
      $category = get_category( get_query_var( 'cat' ) );
      
      if ( $category->parent != 0 ) {
        $html .= custom_get_category_parents( $category->parent );
      }
      
      $html .= '<li class="breadcrumb-item active">' . single_cat_title( '', false ) . '</li>';
    }
    
    elseif ( is_page() && !is_front_page() ) {
      $parent_id = $post->post_parent;
      $parent_pages = array();
      
      while ( $parent_id ) {
        $page = get_page($parent_id);
        $parent_pages[] = $page;
        $parent_id = $page->post_parent;
      }
      
      $parent_pages = array_reverse( $parent_pages );
      
      if ( !empty( $parent_pages ) ) {
        foreach ( $parent_pages as $parent ) {
          $html .= '<li class="breadcrumb-item"><a href="' . esc_url( get_permalink( $parent->ID ) ) . '">' . get_the_title( $parent->ID ) . '</a></li>';
        }
      }
      
      $html .= '<li class="breadcrumb-item active">' . get_the_title() . '</li>';
    }
    
    elseif ( is_singular( 'post' ) ) {
      $categories = get_the_category();
      
      if ( $categories[0] ) {
        $html .= custom_get_category_parents($categories[0]);
      }
      
      $html .= '<li class="breadcrumb-item active">' . get_the_title() . '</li>';
    }
    
    elseif ( is_tag() ) {
      $html .= '<li class="breadcrumb-item active">' . single_tag_title( '', false ) . '</li>';
    }
    
    elseif ( is_day() ) {
      $html .= '<li class="breadcrumb-item"><a href="' . esc_url( get_year_link( get_the_time( 'Y' ) ) ) . '">' . get_the_time( 'Y' ) . '</a></li>';
      $html .= '<li class="breadcrumb-item"><a href="' . esc_url( get_month_link( get_the_time( 'Y' ), get_the_time( 'm' ) ) ) . '">' . get_the_time( 'm' ) . '</a></li>';
      $html .= '<li class="breadcrumb-item active">' . get_the_time('d') . '</li>';
    }
    
    elseif ( is_month() ) {
      $html .= '<li class="breadcrumb-item"><a href="' . esc_url( get_year_link( get_the_time( 'Y' ) ) ) . '">' . get_the_time( 'Y' ) . '</a></li>';
      $html .= '<li class="breadcrumb-item active">' . get_the_time( 'F' ) . '</li>';
    }
    
    elseif ( is_year() ) {
      $html .= '<li class="breadcrumb-item active">' . get_the_time( 'Y' ) . '</li>';
    }
    
    elseif ( is_author() ) {
      $html .= '<li class="breadcrumb-item active">' . get_the_author() . '</li>';
    }
    
    elseif ( is_search() ) {
      
    }
    
    elseif ( is_404() ) {
      
    }
    
  }
  
  $html .= '</ol>';
  
  echo $html;
}