<?php
function closeTags($html) {
    @preg_match_all('#<([a-z]+)(?: .*)?(?<![/|/ ])>#iU', $html, $result);
    $openedtags = $result[1];

    @preg_match_all('#</([a-z]+)>#iU', $html, $result);
    $closedtags = $result[1];

    $len_opened = count($openedtags);
    if (count($closedtags) == $len_opened) {
        return $html;
    }

    $openedtags = array_reverse($openedtags);
    for ($i=0; $i < $len_opened; $i++) {
        if (!in_array($openedtags[$i], $closedtags)) {
            $html .= '</'.$openedtags[$i].'>';
        } else {
            unset($closedtags[array_search($openedtags[$i], $closedtags)]);
        }
    }

    return $html;
}
?>