Taxonomies

Syntax#

register_taxonomy( $taxonomy, $object_type, $args );

Parameters#

Parameter	Details
$taxonomy	(string) (required) The name of the taxonomy. Name should only contain lowercase letters and the underscore character, and not be more than 32 characters long (database structure restriction).
$object_type	(array/string) (required) Name of the object type for the taxonomy object. Object-types can be built-in Post Type or any Custom Post Type that may be registered.
$args	(array/string) (optional) An array of Arguments.
## Example of registering a taxonomy for genres

<?php
// hook into the init action and call create_book_taxonomies when it fires
add_action( 'init', 'create_book_taxonomies', 0 );

// create taxonomy genres for the post type "book"
function create_book_taxonomies() {
    // Add new taxonomy, make it hierarchical (like categories)
    $labels = array(
        'name'              => _x( 'Genres', 'taxonomy general name' ),
        'singular_name'     => _x( 'Genre', 'taxonomy singular name' ),
        'search_items'      => __( 'Search Genres' ),
        'all_items'         => __( 'All Genres' ),
        'parent_item'       => __( 'Parent Genre' ),
        'parent_item_colon' => __( 'Parent Genre:' ),
        'edit_item'         => __( 'Edit Genre' ),
        'update_item'       => __( 'Update Genre' ),
        'add_new_item'      => __( 'Add New Genre' ),
        'new_item_name'     => __( 'New Genre Name' ),
        'menu_name'         => __( 'Genre' ),
    );

    $args = array(
        'hierarchical'      => true,
        'labels'            => $labels,
        'show_ui'           => true,
        'show_admin_column' => true,
        'query_var'         => true,
        'rewrite'           => array( 'slug' => 'genre' ),
    );

    register_taxonomy( 'genre', array( 'book' ), $args );
    
}
?>

You can define custom taxonomies in a themes’s functions.php template file:

Add category in page

You can also add same custom created taxonomy into post type page using below code.

function add_taxonomies_to_pages() {
     register_taxonomy_for_object_type( 'genre', 'page' );
 }
add_action( 'init', 'add_taxonomies_to_pages' );

Add above code into your theme’s functions.php file. Same way you can add custom or default post_tag into post type page.

To get pages using custom taxonomy query need to add below code in same file.

if ( ! is_admin() ) {
     add_action( 'pre_get_posts', 'category_and_tag_archives' );
 }

function category_and_tag_archives( $wp_query ) {
    $my_post_array = array('page');
    if ( $wp_query->get( 'category_name' ) || $wp_query->get( 'cat' ) )
    $wp_query->set( 'post_type', $my_post_array );
}

Add Categories and Tags to Pages and insert them as class into

// add tags and categories to pages

function add_taxonomies_to_pages() {
 register_taxonomy_for_object_type( 'post_tag', 'page' );
 register_taxonomy_for_object_type( 'category', 'page' );
 }
add_action( 'init', 'add_taxonomies_to_pages' );
 if ( ! is_admin() ) {
 add_action( 'pre_get_posts', 'category_and_tag_archives' );
 
 }
function category_and_tag_archives( $wp_query ) {
$my_post_array = array('post','page');
 
 if ( $wp_query->get( 'category_name' ) || $wp_query->get( 'cat' ) )
 $wp_query->set( 'post_type', $my_post_array );
 
 if ( $wp_query->get( 'tag' ) )
 $wp_query->set( 'post_type', $my_post_array );
}

// add tags and categorys as class to <body>

function add_categories_and_tags( $classes = '' ) {
    if( is_page() ) {
        $categories = get_the_category();
        foreach( $categories as $category ) {
            $classes[] = 'category-'.$category->slug;
        }
        $tags = get_the_tags();
        foreach( $tags as $tag ) {
            $classes[] = 'tag-'.$tag->slug;
        }
    }
return $classes;
}
add_filter( 'body_class', 'add_categories_and_tags' );

Add Categories and Tags to Pages and insert as class into

You can add this code to your custom functions.php file:

// add tags and categories to pages

function add_taxonomies_to_pages() {
    register_taxonomy_for_object_type( 'post_tag', 'page' );
    register_taxonomy_for_object_type( 'category', 'page' );
}
add_action( 'init', 'add_taxonomies_to_pages' );

if ( ! is_admin() ) {
    add_action( 'pre_get_posts', 'category_and_tag_archives' );
}
 
function category_and_tag_archives( $wp_query ) {
$my_post_array = array('post','page');

    if ( $wp_query->get( 'category_name' ) || $wp_query->get( 'cat' ) )
    $wp_query->set( 'post_type', $my_post_array );
    
    if ( $wp_query->get( 'tag' ) )
    $wp_query->set( 'post_type', $my_post_array );
    
}

// add tags and categorys as class to <body>

function add_categories_and_tags( $classes = '' ) {
    if( is_page() ) {
        $categories = get_the_category();
        foreach( $categories as $category ) {
            $classes[] = 'category-'.$category->slug;
        }
        $tags = get_the_tags();
        foreach( $tags as $tag ) {
            $classes[] = 'tag-'.$tag->slug;
        }
    }
return $classes;
}
add_filter( 'body_class', 'add_categories_and_tags' );

Works perfect, tested in WordPress 4.8