wp_ajax_add_tag

function wp_ajax_add_tag() {
	check_ajax_referer( 'add-tag', '_wpnonce_add-tag' );
	$taxonomy = ! empty( $_POST['taxonomy'] ) ? $_POST['taxonomy'] : 'post_tag';
	$tax      = get_taxonomy( $taxonomy );

	if ( ! current_user_can( $tax->cap->edit_terms ) ) {
		wp_die( -1 );
	}

	$x = new WP_Ajax_Response();

	$tag = wp_insert_term( $_POST['tag-name'], $taxonomy, $_POST );

	if ( $tag && ! is_wp_error( $tag ) ) {
		$tag = get_term( $tag['term_id'], $taxonomy );
	}

	if ( ! $tag || is_wp_error( $tag ) ) {
		$message = __( 'An error has occurred. Please reload the page and try again.' );

		if ( is_wp_error( $tag ) && $tag->get_error_message() ) {
			$message = $tag->get_error_message();
		}

		$x->add(
			array(
				'what' => 'taxonomy',
				'data' => new WP_Error( 'error', $message ),
			)
		);
		$x->send();
	}

	$wp_list_table = _get_list_table( 'WP_Terms_List_Table', array( 'screen' => $_POST['screen'] ) );

	$level     = 0;
	$noparents = '';

	if ( is_taxonomy_hierarchical( $taxonomy ) ) {
		$level = count( get_ancestors( $tag->term_id, $taxonomy, 'taxonomy' ) );
		ob_start();
		$wp_list_table->single_row( $tag, $level );
		$noparents = ob_get_clean();
	}

	ob_start();
	$wp_list_table->single_row( $tag );
	$parents = ob_get_clean();

	$x->add(
		array(
			'what'         => 'taxonomy',
			'supplemental' => compact( 'parents', 'noparents' ),
		)
	);

	$x->add(
		array(
			'what'         => 'term',
			'position'     => $level,
			'supplemental' => (array) $tag,
		)
	);

	$x->send();
}