درود این تابع کاربردی تمام تگ های بسته نشده HTML رو میبنده:

<?php
    function close_tags($text) {
    $patt_open = "%((?<!</)(?<=<)[\s]*[^/!>\s]+(?=>|[\s]+[^>]*[^/]>)(?!/>))%";
    $patt_close = "%((?<=</)([^>]+)(?=>))%";
    if (preg_match_all($patt_open,$text,$matches))
    {
    $m_open = $matches[1];
    if(!empty($m_open))
    {
    preg_match_all($patt_close,$text,$matches2);
    $m_close = $matches2[1];
    if (count($m_open) > count($m_close))
    {
    $m_open = array_reverse($m_open);
    foreach ($m_close as $tag) $c_tags[$tag]++;
    foreach ($m_open as $k => $tag) if ($c_tags[$tag]--<=0) $text.='</'.$tag.'>';
    }
    }
    }
    return $text;
    }
    ?>