php多语言截取字符串函数

<?php
header("Content-Type:text/html;charset=utf-8");
function msubstr($str, $start = 0, $length, $lenth2, $suffix = true){ 
//$length 中文截取长度，$lenth2英文截取长度 $suffix 是否省略号 
$charset = 'utf-8'; 
if (LANG_SET != 'zh'){ 
    $length = $lenth2; 
} 
$str = preg_replace("/(\<[^\<]*\>|\r|\n|\s|\[.+?\])/is", ' ', $str); 
if (function_exists("mb_substr")) 
    $slice = mb_substr($str, $start, $length, $charset); 
elseif (function_exists('iconv_substr')) { 
    $slice = iconv_substr($str, $start, $length, $charset); 
    if (false === $slice) { 
        $slice = ''; 
    } 
} else { 
    $re['utf-8'] = "/[\x01-\x7f]|[\xc2-\xdf][\x80-\xbf]|[\xe0-\xef][\x80-\xbf]{2}|[\xf0-\xff][\x80-\xbf]{3}/"; 
    $re['gb2312'] = "/[\x01-\x7f]|[\xb0-\xf7][\xa0-\xfe]/"; 
    $re['gbk'] = "/[\x01-\x7f]|[\x81-\xfe][\x40-\xfe]/"; 
    $re['big5'] = "/[\x01-\x7f]|[\x81-\xfe]([\x40-\x7e]|\xa1-\xfe])/"; 
    preg_match_all($re[$charset], $str, $match); 
    $slice = join("", array_slice($match[0], $start, $length)); 
} 
$fix = ''; 
if (LANG_SET == 'zh') { 
    $slice = str_replace(' ', '', $slice); 
    if (strlen($slice) > $length) { 
        $fix = '...'; 
    } 
} else { 
    if (strlen($str) > $lenth2) { 
        $fix = '...'; 
    } 
} 
return $suffix ? $slice . $fix : $slice; 
}

$str = "dsd个法师dsad打发dd的撒ddsddsadsadsads的撒";

echo msubstr($str,1,2,20,true);

?>