Leading zeros in WooCommerce order number

functions.php

add_filter( 'woocommerce_order_number', 'swp_woocommerce_order_number_leading_zeros', 10 );
function swp_woocommerce_order_number_leading_zeros( $order_id ) {
    $max_length = 8;
    $new_order_id = str_pad( $order_id, $max_length, '0', STR_PAD_LEFT );
    return $new_order_id;
}