taxonomy_node_count.php

<?php
/**
 * @param tid
 *   Term ID
 * @param child_count
 *   TRUE - Also count all nodes in child terms (if they exists) - Default
 *   FALSE - Count only nodes related to Term ID
 */
function term_nc($tid, $child_count = TRUE) {
  $tids = array($tid);

  if ($child_count) {
    $tids = array_merge($tids, term_get_children_ids($tid));
  }

  global $language;
  $langs = array($language->language);
  $langs[] = 'und';

  $query = db_select('taxonomy_index', 't');
  $query->condition('tid', $tids, 'IN');
  $query->join('node', 'n', 't.nid = n.nid');
  $query->condition('n.status', 1, '=');
  $query->condition('n.language', $langs, 'IN');

  $count = $query->countQuery()->execute()->fetchField();
  return  $count;
}

/**
 * Retrieve ids of term children .
 *
 * @param $tid
 *   The term's ID.
 * @param $tids
 *   An array where ids of term children will be added
 */
function term_get_children_ids($tid) {
  $children = taxonomy_get_children($tid);
  $tids=array();

  if (!empty($children)) {
    foreach($children as $child) {
      $tids[] = $child->tid;
      $tids = array_merge($tids, term_get_children_ids($child->tid));
    }
  }
  return $tids;
}