php smarty truncate UTF8乱码问题解决办法

<?php
/**
 * Smarty plugin
 * @package Smarty
 * @subpackage plugins
 */

 
/**
 * Smarty truncate modifier plugin
 *
 * Type:     modifier<br>
 * Name:     truncate<br>
 * Purpose:  Truncate a string to a certain length if necessary,
 *           optionally splitting in the middle of a word, and
 *           appending the $etc string or inserting $etc into the middle.
 * @link http://smarty.php.net/manual/en/language.modifier.truncate.php
 *          truncate (Smarty online manual)
 * @author   Monte Ohrt <monte at ohrt dot com>
 * @param string
 * @param integer
 * @param string
 * @param boolean
 * @param boolean
 * @return string
 */
function smarty_modifier_truncate2( $string,$length = 80,$etc='...',$count_words = true ) {
 return $returnstr =substr_utf8($string, 0, $length).$etc;

}

function substr_utf8($str, $start=0, $length=-1, $return_ary=false) {
    $len = strlen($str);if ($length == -1) $length = $len;
    $r = array();
    $n = 0;
    $m = 0;

    for($i = 0; $i < $len; $i++) {
        $x = substr($str, $i, 1);
        $a = base_convert(ord($x), 10, 2);
        $a = substr('00000000'.$a, -8);
        if ($n < $start) {
            if (substr($a, 0, 1) == 0) {
            }elseif (substr($a, 0, 3) == 110) {
                $i += 1;
            }elseif (substr($a, 0, 4) == 1110) {
                $i += 2;
            }
            $n++;
        }else {
            if (substr($a, 0, 1) == 0) {
                $r[] = substr($str, $i, 1);
            }elseif (substr($a, 0, 3) == 110) {
                $r[] = substr($str, $i, 2);
                $i += 1;
            }elseif (substr($a, 0, 4) == 1110) {
                $r[] = substr($str, $i, 3);
                $i += 2;
            }else {
                $r[] = '';
            }
            if (++$m >= $length) {
                break;
            }
        }
    }

    return $return_ary ? $r : implode("",$r);
}
/* vim: set expandtab: */
?>