Open closed HTML tags

opentags.php

<?php

function opentags($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];

    $len_closed = count($closedtags);
    if (count($openedtags) == $len_closed) {
        return $html;
    }
    
    $tags = '';
    $openedtags_occurences = array_count_values($openedtags);
    $closedtags_occurences = array_count_values($closedtags);

    $closedtags = array_reverse($closedtags);
    foreach ($closedtags as $tag) {
      if (isset($openedtags_occurences[$tag]) && $openedtags_occurences[$tag] < $closedtags_occurences[$tag]) {
        $tags.= '<'.$tag.'>';
        ++ $openedtags_occurences[$tag];
      } elseif ( ! isset($openedtags_occurences[$tag])) {
        $tags.= '<'.$tag.'>';
        $openedtags_occurences[$tag] = 1;
      } 
    }
    return $tags.$html;
}