[Gravity Forms] Custom Merge Tags

functions.php

<?php
add_filter('gform_custom_merge_tags', 'ching_custom_merge_tags', 10, 4);
function ching_custom_merge_tags( $merge_tags, $form_id, $fields, $element_id ) {
  $merge_tags[] = array('label' => 'Open Present', 'tag' => '{open_present}');
  return $merge_tags;
}
add_filter('gform_replace_merge_tags', 'ching_replace_merge_tags', 10, 3);
function ching_replace_merge_tags( $text, $form, $entry ) {
  if ( strpos( $text, '{open_present}' ) ) {
    $text = str_replace( '{open_present}', 'Here it is!', $text );
  }
  return $text;
}