drupal_set_title.php

<?php
  // Set page title, if exist.
  if (isset($page['#page_title'])) {

    // Check for title output flag.
    if (!isset($page['#page_title_output']) || !in_array($page['#page_title_output'], array(CHECK_PLAIN, PASS_THROUGH))) {
      $page['#page_title_output'] = CHECK_PLAIN;
    }

    drupal_set_title($page['#page_title'], $page['#page_title_output']);
  }
?>