HTML タグの補完と Web コンテンツのフィルタリングを実装する PHP メソッド

function closetags($html) {
 preg_match_all(&#39;#<(?!meta|img|br|hr|input\b)\b([a-z]+)(?: .*)?(?<![/|/ ])>#iU&#39;, $html, $result);
 $openedtags = $result[1];
 preg_match_all(&#39;#</([a-z]+)>#iU&#39;, $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)) {
     $html .= &#39;</&#39;.$openedtags[$i].&#39;>&#39;;
    }else {
     unset($closedtags[array_search($openedtags[$i], $closedtags)]);
    }
 }
 return $html;
}

function checkhtml($html) {
  $html = stripslashes($html);
    preg_match_all("/\<([^\<]+)\>/is", $html, $ms);
    $searchs[] = &#39;<&#39;;
    $replaces[] = &#39;<&#39;;
    $searchs[] = &#39;>&#39;;
    $replaces[] = &#39;>&#39;;
    if($ms[1]) {
      $allowtags = &#39;img|font|p|table|tbody|tr|td|th|br|p|b|strong|i|u|em|span|ol|ul|li&#39;;//允许的标签
      $ms[1] = array_unique($ms[1]);
      foreach ($ms[1] as $value) {
        $searchs[] = "<".$value.">";
        $value = shtmlspecialchars($value);
        $value = str_replace(array(&#39;\\&#39;,&#39;/*&#39;), array(&#39;.&#39;,&#39;/.&#39;), $value);
        $value = preg_replace(array("/(javascript|script|eval|behaviour|expression)/i", "/(\s+|"|&#39;)on/i"), array(&#39;.&#39;, &#39; .&#39;), $value);
        if(!preg_match("/^[\/|\s]?($allowtags)(\s+|$)/is", $value)) {
          $value = &#39;&#39;;
        }
        $replaces[] = empty($value)?&#39;&#39;:"<".str_replace(&#39;"&#39;, &#39;"&#39;, $value).">";
      }
    }
    $html = str_replace($searchs, $replaces, $html);
  return $html;
}
//取消HTML代码
function shtmlspecialchars($string) {
  if(is_array($string)) {
    foreach($string as $key => $val) {
      $string[$key] = shtmlspecialchars($val);
    }
  } else {
    $string = preg_replace(&#39;/&((#(\d{3,5}|x[a-fA-F0-9]{4})|[a-zA-Z][a-z0-9]{2,5});)/&#39;, &#39;&\\1&#39;,
      str_replace(array(&#39;&&#39;, &#39;"&#39;, &#39;<&#39;, &#39;>&#39;), array(&#39;&&#39;, &#39;"&#39;, &#39;<&#39;, &#39;>&#39;), $string));
  }
  return $string;
}