Wordpress: Admin Filter Posts by Taxonomy

filter-by-tax.php

<?php

function restrict_posts_by_tax() {
	global $typenow;
	$post_type = 'books'; // change HERE
	$taxonomy = 'genre'; // change HERE
	if ($typenow == $post_type) {
		$selected = isset($_GET[$taxonomy]) ? $_GET[$taxonomy] : '';
		$info_taxonomy = get_taxonomy($taxonomy);
		wp_dropdown_categories(array(
			'show_option_all' => __("Show All {$info_taxonomy->label}"),
			'taxonomy' => $taxonomy,
			'name' => $taxonomy,
			'orderby' => 'name',
			'selected' => $selected,
			'show_count' => true,
			'hide_empty' => true,
		));
	};
}
add_action('restrict_manage_posts', 'restrict_posts_by_tax');

function convert_id_to_term_in_query($query) {
	global $pagenow;
	$post_type = 'books'; // change HERE
	$taxonomy = 'genre'; // change HERE
	$q_vars = &$query->query_vars;
	if ($pagenow == 'edit.php' && isset($q_vars['post_type']) && $q_vars['post_type'] == $post_type && isset($q_vars[$taxonomy]) && is_numeric($q_vars[$taxonomy]) && $q_vars[$taxonomy] != 0) {
		$term = get_term_by('id', $q_vars[$taxonomy], $taxonomy);
		$q_vars[$taxonomy] = $term->slug;
	}
}
add_filter('parse_query', 'convert_id_to_term_in_query');

?>