Add 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 );
}