PHP截取字符串长度

<?php

function str_cut($string, $start=0,$length, $dot = '..') {
    $strlen = strlen($string);
    if($strlen <= $length) return $string;
    $string = str_replace(array('&nbsp;', '&amp;', '&quot;', '&#039;', '&ldquo;', '&rdquo;', '&mdash;', '&lt;', '&gt;', '&middot;', '&hellip;'), array(' ', '&', '"', "'", '“', '”', '—', '<', '>', '·', '…'), $string);
    $strcut = '';
    $n = $tn = $noc = 0;
    while($n < $strlen) {
        $t = ord($string[$n]);
        if($t == 9 || $t == 10 || (32 <= $t && $t <= 126)) {
            $tn = 1; $n++; $noc++;
        } elseif(194 <= $t && $t <= 223) {
            $tn = 2; $n += 2; $noc += 2;
        } elseif(224 <= $t && $t < 239) {
            $tn = 3; $n += 3; $noc += 2;
        } elseif(240 <= $t && $t <= 247) {
            $tn = 4; $n += 4; $noc += 2;
        } elseif(248 <= $t && $t <= 251) {
            $tn = 5; $n += 5; $noc += 2;
        } elseif($t == 252 || $t == 253) {
            $tn = 6; $n += 6; $noc += 2;
        } else {
            $n++;
        }
        if($noc >= $length) break;
    }
    if($noc > $length) $n -= $tn;
    $strcut = substr($string, $start, $n);
    $strcut = str_replace(array('&', '"', "'", '<', '>'), array('&amp;', '&quot;', '&#039;', '&lt;', '&gt;'), $strcut);
    if( $strlen==strlen($strcut)){
        return $strcut;
    }else{
        return $strcut.$dot;
    }

}

echo str_cut("首页显示标题太长了就会把表格撑破比较难看谁能帮我写一段代码",0,14,'...');

/*或者使用mb_substr函数  

用法如：

mb_substr("首页显示标题太长了就会把表格撑破比较难看谁能帮我写一段代码",0,14,'utf-8');

mb_substr("首页显示标题太长了就会把表格撑破比较难看谁能帮我写一段代码",0,14,'gbk');

*/

?>