php汉字截取

/**
 * 截取HTML,并自动补全闭合
 * @param $html
 * @param $length
 * @param $end
 */
function subHtml($html,$length,$charset) {
    $result = '';
    $tagStack = array();
    $len = 0;    
    $contents = preg_split("~(<[^>]+?>)~si",$html, -1,PREG_SPLIT_NO_EMPTY| PREG_SPLIT_DELIM_CAPTURE);

    foreach($contents as $tag)
    {
        
        if (trim($tag)=="") 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, $charset) < $length){
                $result .= $tag;
                $len += mstrlen($tag, $charset); 
            }else {
                $str = msubstr($tag,0,$length-$len+1,'', $charset);
                $result .= $str;
                break;
            }
        }
    }
        
    while(!empty($tagStack)){        
        $result .= '</'.array_pop($tagStack).'>';
    }
    
        
    return $result;
}

/**
 * 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); 
        $length=count($ar[0]);
    }
    return $length;
}

/**
 * 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;
}