字符串切割函数，一个字母算一个位置,一个字算2个位置

function str_cut($string, $length, $dot = '') {
    $string = str_replace(array(
        ' ', '&', '"', ''', '“', '”', '—', '<', '>',
        '·', '…'
            ), array(' ', '&', '"', "'", '“', '”', '—', '<', '>', '·', '…'), $string);
    $strlen = strlen($string);
    if ($strlen <= $length)
        return $string;
    $maxi = $length - strlen($dot);
    $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 >= $maxi)
            break;
    }
    if ($noc > $maxi)
        $n -= $tn;
    $strcut = substr($string, 0, $n);
    $strcut = str_replace(array('&', '"', "'", '<', '>'), array('&amp;', '&quot;', '&#039;', '&lt;', '&gt;'), $strcut);
    return $strcut . $dot;
}

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