Артем Золин

if ( ! function_exists( 'get_wpgen_header_classes' ) ) {

	/**
	 * Get classes for header container.
	 *
	 * @param string $class Additional header classes.
	 *
	 * @return array
	 */
	function get_wpgen_header_classes( $class = '' ) {

		// Add elements to array.
		$classes   = array();
		$classes[] = 'header';

		if ( has_custom_header() ) {
			$classes[] = 'header--background-image';
		}

		if ( is_front_page() || is_home() ) {
			$classes[] = 'header-bg';
		} else {
			$classes[] = 'custom-class';
		}

		// Check the function has accepted any classes.
		if ( isset( $class ) && ! empty( $class ) ) {
			if ( is_array( $class ) ) {
				$classes = array_merge( $classes, $class );
			} elseif ( is_string( $class ) ) {
				$classes = array_merge( $classes, explode( ' ', $class ) );
			}
		}

		$classes = apply_filters( 'get_wpgen_header_classes', $classes );

		// Usage:
		/*add_filter( 'get_wpgen_header_classes', 'my_header_classes' );
		if ( ! function_exists( 'my_header_classes' ) ) {
			function my_header_classes( $classes ) {
				$classes[] = 'my-class';
				return array_unique( $classes );
			}
		}*/

		return array_unique( (array) $classes );
	}
}

if ( ! function_exists( 'wpgen_header_classes' ) ) {

	/**
	 * Display classes for header container.
	 *
	 * @param string $class Additional header classes.
	 * @param bool   $echo  Echo or return header classes.
	 *
	 * @return string
	 */
	function wpgen_header_classes( $class = '', $echo = true ) {

		$classes = get_wpgen_header_classes( $class );

		if ( $echo ) {
			echo 'class="' . esc_attr( implode( ' ', $classes ) ) . '"';
		} else {
			return 'class="' . esc_attr( implode( ' ', $classes ) ) . '"';
		}
	}
}

<header id="header" <?php wpgen_header_classes(); ?>>

<header id="header" <?php wpgen_header_classes( 'new-class' ); ?>>

if ( $cat->parent === 0 ) {
	# родительская категория.
} else {
	# дочерняя категория.
}

Из-за чего на сайте могут не работать переходы между городами в шапке?

function get_yoast_custom_title() {

	if ( is_single() ) {
		$string = get_the_title();
	} else {
		$string = 'Заголовок по умолчанию';
	}

	return $string;
}


// Define the action for register yoast_variable replacments.
function register_custom_yoast_variables() {
	wpseo_register_var_replacement( '%%CustomTitle%%', 'get_yoast_custom_title', 'advanced', __( 'Some instead title text', 'wpgen' ) );
}

// Add action.
add_action( 'wpseo_register_extra_replacements', 'register_custom_yoast_variables' );

function get_category_post_count() {

	$string = '';

	if ( is_category() && isset( get_queried_object()->count ) ) {
		$string = get_queried_object()->count;
	}

	return $string;
}


// Define the action for register yoast_variable replacments.
function register_custom_yoast_variables() {
	wpseo_register_var_replacement( '%%PostCount%%', 'get_category_post_count', 'advanced', __( 'Some instead title text', 'wpgen' ) );
}

// Add action.
add_action( 'wpseo_register_extra_replacements', 'register_custom_yoast_variables' );

add_action( 'init', 'education_register_post_type' );
function education_register_post_type() {

	// Taxonomy repetitor_cat.
	register_taxonomy( 'repetitor_cat', array( 'repetitor' ), array(
		'labels'             => array(
			'name'              => _x( 'Repetitor category', 'taxonomy general name', 'education' ),
			'singular_name'     => _x( 'Repetitor categories', 'taxonomy singular name', 'education' ),
			'search_items'      => __( 'Search Repetitor category', 'education' ),
			'popular_items'     => __( 'Popular Repetitor category', 'education' ),
			'all_items'         => __( 'All Repetitor categories', 'education' ),
			'parent_item'       => null,
			'parent_item_colon' => null,
			'edit_item'         => __( 'Edit Repetitor category', 'education' ),
			'update_item'       => __( 'Update Repetitor category', 'education' ),
			'add_new_item'      => __( 'Add new Repetitor category', 'education' ),
			'new_item_name'     => __( 'New Repetitor category name', 'education' ),
			'menu_name'         => __( 'Repetitor categories', 'education' ),
		),
		'public'             => true,
		'show_tagcloud'      => true,
		'hierarchical'       => false,
		'query_var'          => true,
		'show_in_quick_edit' => true,
		'sort'               => true,
	) );

	// Post type repetitor.
	register_post_type( 'repetitor', array(
		'labels'          => array(
			'name'               => __( 'Repetitors', 'education' ),
			'singular_name'      => __( 'Repetitor', 'education' ),
			'add_new'            => __( 'Add Repetitor', 'education' ),
			'add_new_item'       => __( 'Add new Repetitor', 'education' ),
			'edit_item'          => __( 'Edit Repetitor', 'education' ),
			'new_item'           => __( 'New Repetitor', 'education' ),
			'view_item'          => __( 'View Repetitor', 'education' ),
			'search_items'       => __( 'Search Repetitor', 'education' ),
			'not_found'          => __( 'Repetitor not found', 'education' ),
			'not_found_in_trash' => __( 'Repetitor not found in trash', 'education' ),
			'menu_name'          => __( 'Repetitors', 'education' ),
		),
		'public'          => true,
		'show_in_rest'    => true, // Включает Gutenberg.
		'capability_type' => 'post',
		'hierarchical'    => false,
		'has_archive'     => 'repetitors',
		'rewrite'         => array( 'slug' => 'repetitors', 'with_front' => false, 'pages' => true, 'feeds' => false, 'feed' => false ),
		'query_var'       => true,
		'supports'        => array( 'page-attributes', 'title', 'editor', 'author', 'thumbnail', 'excerpt', 'comments', 'custom-fields' ),
		'taxonomies'      => array( 'repetitor_cat' ),
	) );
}