EDIT

/**

 * @todo Please document this function.

 * @see http://drupal.org/node/1354

 */

function theme_cdm_back_to_search_result_button() {

  $out = '';

  $show_button = variable_get('cdm_dataportal_show_back_to_search_results');

  if (isset($_SESSION['cdm']['search']) && isset($show_button) &&  $show_button == 1) {

    /* ['cdm']['last_search'] */

    // $out .= '<div id="backButton">'.l(t('Back to search result'), $_SESSION

    // ).'</div>';

    $out .= '<div id="backButton" class="clearfix">' . l(t('Back to search result'), "http://" . $_SERVER['SERVER_NAME'] . $_SESSION['cdm']['last_search']) . '</div>';

  }

  return $out;

}