function CloseTags($html)
{
  // strip fraction of open or close tag from end (e.g. if we take first x characters, we might cut off a tag at the end!)
  $html = preg_replace('/<[^>]*$/','',$html); // ending with fraction of open tag
  // put open tags into an array
  preg_match_all('#<([a-z]+)(?: .*)?(?<![/|/ ])>#iU', $html, $result);
  $opentags = $result[1];
  // put all closed tags into an array
  preg_match_all('#</([a-z]+)>#iU', $html, $result);
  $closetags = $result[1];
  $len_opened = count($opentags);
  // if all tags are closed, we can return
  if (count($closetags) == $len_opened) {
   return $html;
  }
  // close tags in reverse order that they were opened
  $opentags = array_reverse($opentags);
  // self closing tags
  $sc = array('br','input','img','hr','meta','link');
  // ,'frame','iframe','param','area','base','basefont','col'
  // should not skip tags that can have content inside!
  for ($i=0; $i < $len_opened; $i++)
  {
   $ot = strtolower($opentags[$i]);
   if (!in_array($opentags[$i], $closetags) && !in_array($ot,$sc))
   {
    $html .= '</'.$opentags[$i].'>';
   }
   else
   {
    unset($closetags[array_search($opentags[$i], $closetags)]);
   }
  }
  return $html;
}

<?php
$content = '<div><p><span>越發(fā)忙碌的你，是否想給自己放個假？專注工作的你，是否還記得上一次鍛煉是什么時候？優(yōu)伴戶外旅行，給你不一樣的旅行體驗：給心自由，便處處都是風景！';
echo CloseTags($content);
/*
返回的結果是:
<div><p><span>
越發(fā)忙碌的你，是否想給自己放個假？專注工作的你，是否還記得上一次鍛煉是什么時候？優(yōu)伴戶外旅行，給你不一樣的旅行體驗：給心自由，便處處都是風景！</span></p></div>
*/
?>