WordPress - Add custom taxonomy filters to custom post types

gistfile1.php

<?php

// Add category filters to WP custom post types
add_action( 'restrict_manage_posts', 'my_add_category_filters' );
function my_add_category_filters() {
	global $typenow;
	if( $typenow == "event" ){
		$taxonomy = 'event_type';
	}
	elseif( $typenow == "guideline" ){
		$taxonomy = 'guideline_type';
	}
	elseif( $typenow == "resource" ){
		$taxonomy = 'resource_type';
	}
	if( $typenow != "post" && $typenow != "page" ) {
		$filters = array($taxonomy);
		foreach ($filters as $tax_slug) {
			$tax_obj = get_taxonomy($tax_slug);
			$tax_name = $tax_obj->labels->name;
			$terms = get_terms($tax_slug);
			echo "<select name='$tax_slug' id='$tax_slug' class='postform'>";
			echo "<option value=''>View all categories</option>";
			foreach ($terms as $term) { echo '<option value='. $term->slug, $_GET[$tax_slug] == $term->slug ? ' selected="selected"' : '','>' . $term->name .' (' . $term->count .')</option>'; }
			echo "</select>";
		}
	}
}


?>