Update description on payment page for Mastercard (MPGS) for Give

mastercard-update-description.php

<?php
function mg_update_payment_description( $text, $donationId ) {
  $donation_type = give_get_meta( $donationId, 'donation_type', true ); // `donation_type` is the custom field key added by the Form Field Manager.

  return "{$text} - {$donation_type}";
}

add_filter( 'mgmcfg_update_form_description', 'mg_update_payment_description', 10, 2 );