how to merge with flatforum's template.php?

I have Drupal 4.7.6 with flatforum 4.7.x-1.x-dev http://drupal.org/project/flatforum and now I install the latest taxonomy_image module for 4.7.x. But I need help with merging the taxonomy_image function _phptemplate_variables with the function with the same name that already exists in flatforum's themes/my_theme/template.php.

flatforum's template.php looks like this:

<?php
// $Id: template.php,v 1.7 2006/05/11 18:17:29 ayman Exp $

function _phptemplate_variables($hook, $vars) {
  static $is_forum;
  $variables = array();
  if (!isset($is_forum)) {
    if (arg(0) == 'node' && is_numeric(arg(1)) && arg(2) == '') {
      $nid = arg(1);
    }
    if (arg(0) == 'comment' && arg(1) == 'reply' && is_numeric(arg(2))) {
      $nid = arg(2);
    }
    if ($nid) {
      $node = node_load(array('nid' => $nid));
    }
    $is_forum = ($node && $node->type == 'forum');
    _is_forum($is_forum);
  }
  if ($is_forum) {
    switch ($hook) {
      case 'comment' :
        $variables['template_file'] = 'node-forum';
        $variables['row_class'] = _row_class();
        $variables['name'] = $vars['author'];
        $variables['userid'] = $vars['comment']->uid;
        $joined = module_invoke('flatforum', 'get_created', $vars['comment']->uid);
        $variables['joined'] = $joined ? format_date($joined, 'custom', 'Y-m-d') : '';
        $posts = module_invoke('flatforum', 'get', $vars['comment']->uid);
        $variables['posts'] = $posts ? $posts : 0;
        $variables['submitted'] = format_date($vars['comment']->timestamp);
        $subject = $vars['comment']->subject;
        $variables['title'] = empty($subject) ? '&nbsp' : $subject;
        $variables['content'] = $vars['comment']->comment;
        $variables['links'] = empty($vars['links']) ? '&nbsp' : $vars['links'];
        break;
      case 'node' :
        $variables['row_class'] = _row_class();
        $variables['userid']=$vars['node']->uid;
        $joined = module_invoke('flatforum', 'get_created', $vars['node']->uid);
        $variables['joined'] = $joined ? format_date($joined, 'custom', 'Y-m-d') : '';
        $posts = module_invoke('flatforum', 'get', $vars['node']->uid);
        $variables['posts'] = $posts ? $posts : 0;
        $variables['title'] = empty($vars['title']) ? '&nbsp' : $vars['title'];
        $variables['content'] = $vars['node']->body;
        $variables['links'] = empty($vars['links']) ? '&nbsp' : $vars['links'];
        break;
    }
  }
  return $variables;
}
function _row_class() {
  static $forum_row = TRUE;
  $forum_row = !$forum_row;
  return $forum_row ? 'odd' : 'even';
}
function _is_forum($arg = NULL) {
  static $is_forum = FALSE;
  if ($arg) {
    $is_forum = $arg;
  }
  return $is_forum;
}
?>

i've tried several arrangements to merge the function _phptemplate_variables for taxonomy_image but the code either slams the look of the flatforums or the taxonomy_images do not appear on the nodes.

Here is the code I need to merge with flatforum's template.php above:

function _phptemplate_variables($hook, $vars) {
  if ($hook == 'node') {
    if (module_exist("taxonomy_image")) {
       foreach (taxonomy_node_get_terms($vars['node']->nid) as $term) {
        $vars['taxonomy_images'][] = taxonomy_image_display($term->tid, "alt='$term->name'");
       }
    }
  }
return $vars;
}

Thank you for any advice!