php截取html字符串自动补全html标签

 $contents = preg_split("~(<[^>]+?>)~si",$html, -1,PREG_SPLIT_NO_EMPTY| PREG_SPLIT_DELIM_CAPTURE);
 foreach($contents as $tag)
 {
 if (trim($tag)=="")&nbsp; continue;
 if(preg_match("~<([a-z0-9]+)[^/>]*?/>~si",$tag)){
 $result .= $tag;
 }else if(preg_match("~</([a-z0-9]+)[^/>]*?>~si",$tag,$match)){
 if($tagStack[count($tagStack)-1] == $match[1]){
 array_pop($tagStack);
 $result .= $tag;
 }
 }else if(preg_match("~<([a-z0-9]+)[^/>]*?>~si",$tag,$match)){
 array_push($tagStack,$match[1]);
 $result .= $tag;
 }else if(preg_match("~<!--.*?-->~si",$tag)){
 $result .= $tag;
 }else{
 if($len + mstrlen($tag) < $length){
 $result .= $tag;
 $len += mstrlen($tag);
 }else {
 $str = msubstr($tag,0,$length-$len+1);
 $result .= $str;
 break;
 }

 }
 }
 while(!empty($tagStack)){
 $result .= '</'.array_pop($tagStack).'>';
 }
 return&nbsp; $result;
}

/**
 * 截取中文字符串
 * @param $string 字符串
 * @param $start 起始位
 * @param $length 长度
 * @param $charset&nbsp; 编码
 * @param $dot 附加字串
 */
function msubstr($string, $start, $length,$dot='',$charset = 'UTF-8') {
 $string = str_replace(array('&amp;', '&quot;', '&lt;', '&gt;','&nbsp;'), array('&', '"', '<', '>',' '), $string);
 if(strlen($string) <= $length) {
 return $string;
 }

 if(strtolower($charset) == 'utf-8') {
 $n = $tn = $noc = 0;
 while($n < strlen($string)) {
 $t = ord($string[$n]);
 if($t == 9 || $t == 10 || (32 <= $t && $t <= 126)) {
 $tn = 1; $n++;
 } elseif(194 <= $t && $t <= 223) {
 $tn = 2; $n += 2;
 } elseif(224 <= $t && $t <= 239) {
 $tn = 3; $n += 3;
 } elseif(240 <= $t && $t <= 247) {
 $tn = 4; $n += 4;
 } elseif(248 <= $t && $t <= 251) {
 $tn = 5; $n += 5;
 } elseif($t == 252 || $t == 253) {
 $tn = 6; $n += 6;
 } else {
 $n++;
 }
 $noc++;
 if($noc >= $length) {
 break;
 }
 }
 if($noc > $length) {
 $n -= $tn;
 }
 $strcut = substr($string, 0, $n);
 } else {
 for($i = 0; $i < $length; $i++) {
 $strcut .= ord($string[$i]) > 127 ? $string[$i].$string[++$i] : $string[$i];
 }
 }

 return $strcut.$dot;
}

/**
 * 取得字符串的长度，包括中英文。
 */
function mstrlen($str,$charset = 'UTF-8'){
 if (function_exists('mb_substr')) {
 $length=mb_strlen($str,$charset);
 } elseif (function_exists('iconv_substr')) {
 $length=iconv_strlen($str,$charset);
 } else {
 preg_match_all("/[x01-x7f]|[xc2-xdf][x80-xbf]|xe0[xa0-xbf][x80-xbf]|[xe1-xef][x80-xbf][x80-xbf]|xf0[x90-xbf][x80-xbf][x80-xbf]|[xf1-xf7][x80-xbf][x80-xbf][x80-xbf]/", $text, $ar);&nbsp;
 $length=count($ar[0]);
 }
 return $length;
}

          if(ord($str[$i])>128)
          {
            //$re.=substr($str,$i,3);
            $i+=3;
            $word++;
          }
          else if ($str[$i]=='<')
          {
              if ($str[$i+1] == '!')
              {
                $i++;
                  continue;
              }

              if ($str[$i+1]=='/')   
              {
                $ptag=&$etag ;
                $k=&$ep;
                $i+=2;
              }
              else                   
              {
                $ptag=&$stag;
                $i+=1;
                $k=&$sp;
              }

              for(;$i<$leng;$i++)       
              {
                  if ($str[$i] == ' ')
                  {
                    $ptag[$k] = implode('',$ptag[$k]);
                    $k++;
                      break;
                  }
                  if ($str[$i] != '>')
                  {
                    $ptag[$k][]=$str[$i];
                      continue;
                  }
                  else               
                  {
                    $ptag[$k] = implode('',$ptag[$k]);
                    $k++;
                      break;
                  }
              }
            $i++;
              continue;
          }
          else
          {
            //$re.=substr($str,$i,1);
            $word++;
            $i++;
          }
      }
      foreach ($etag as $val)
      {
        $key1=array_search($val,$stag);
          if ($key1 !== false)          unset($stag[$key]);
      }
      foreach ($stag as $key => $val)
      {
          if (in_array($val,array('br','img'))) unset($stag[$key1]);
      }
    array_reverse($stag);
    $ends = '</'.implode('></',$stag).'>';
    $re = substr($str,0,$i).$ends;
      if($more)    $re.='...';
      return $re;
}