Generate taxonomy filters Class

class FGW_CPT_Taxonomy_Filter{

    /**
     * The custom post type to alter and the taxonomies to show filters for
     *
     * @var array
     */
    private $cpt = array();

    /**
     * Constructor
     *
     * @param required array $cpt   The custom post type and associated taxonomies to show filters for (as "array($cpt => array(tax1, tax2))")
     */
    public function __construct($cpt = array()){

        $this->cpt = $cpt;
        add_action('restrict_manage_posts', array($this, 'render_filter'));

    }

    /**
     * Render the taxonomy filter
     */
    public function render_filter(){

        global $typenow;

        $types = array_keys($this->cpt);        // Grab the post types that are being edited

        if(in_array($typenow, $types)):         // Check to see if the page now is one of the custom post types supplied by the user

            $filters = $this->cpt[$typenow];    // Grab all of the taxonomies that shold have a filter

            foreach($filters as $tax_slug) :

                $tax_obj = get_taxonomy($tax_slug); // Grab the taxonomy object (from the taxonomy slug)

                $dropdown_args = array(             // Output the filter dropdown
                    'show_option_all' =>  $tax_obj->labels->all_items,
                    'taxonomy'      =>  $tax_slug,
                    'name'          =>  $tax_slug,
                    'orderby'        =>  'name',
                    'selected'      =>  (isset($_GET[$tax_slug]) ? $_GET[strtolower($tax_slug)] : null),
                    'hierarchical'  =>  true,
                    'depth'        =>  0,
                    'show_count'      =>  false,
                    'hide_empty'      =>  false
                );
                wp_dropdown_categories($dropdown_args);

            endforeach;

        endif;

    }

}