Close opened HTML tags

closetags.php

<?php

function closetags($html) {
    preg_match_all('#<(?!meta|img|br|hr|input\b)\b([a-z]+)(?: .*)?(?<![/|/ ])>#iU', $html, $result);
    $openedtags = $result[1];
    preg_match_all('#</([a-z]+)>#iU', $html, $result);
    $closedtags = $result[1];

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

    $openedtags = array_reverse($openedtags);
    foreach ($openedtags as $tag) {
      if ( ! in_array($tag, $closedtags)) {
        $html .= '</'.$tag.'>';
      } else {
        unset($closedtags[array_search($tag, $closedtags)]);
      }
    }
    return $html;
}