Order terms by name cast as a number. Originally used for retrieving WooCommerce attributes. To use, set the 'orderby' argument in your `get_terms` call to 'name_as_number'.

get_terms_orderby_name_as_number

add_filter( 'get_terms_orderby', 'slimline_get_terms_orderby_name_as_number', 10, 2 );

/**
 * slimline_get_terms_orderby_name_as_number function
 *
 * @param string $orderby The orderby string created from the initial arguments passed through `get_terms`
 * @param array $args `get_terms` arguments
 * @return string $orderby Name cast as a number if `orderby` is 'name_as_number', otherwise unchanged
 */
function slimline_get_terms_orderby_name_as_number( $orderby, $args ) {

	if ( 'name_as_number' === $args[ 'orderby' ] ) {
		$orderby = 't.name+0';
	} // if ( 'name_as_number' === $args[ 'orderby' ] )

	return $orderby;
}