php截取字符串，兼容utf8、gb2312，gbk、big5

<?php

function CsubStrPro($str, $start = 0, $length, $charset = "utf-8", $suffix = true)
{
if (function_exists ( "mb_substr" ))
return mb_substr ( $str, $start, $length, $charset );
$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, $length ) );
if ($suffix)
return $slice ;
return $slice;

}

$content=CsubStrPro($str,0,129,'gbk');
?>