php 截取字符串，支持中文无乱码

<?php

$charset = 'utf-8';

function subistr($string, $length, $dot = ' ...') {

global $charset;

if(strlen($string) <= $length) {

return $string;

}

$s = '';

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++; $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;

}

$s = substr($string, 0, $n);

} else {

for($i = 0; $i < $length; $i++) {

$s .= ord($string[$i]) >= 127 ? $string[$i].$string[++$i] : $string[$i];

}

}

return $s.$dot;

}