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//----------------------------------------------------------------------------------
// 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 );
}