PHP小程序--字符串截取，支持中文和其他编码

<?php
/**
 +----------------------------------------------------------
 * 字符串截取，支持中文和其他编码
 +----------------------------------------------------------
 * @static
 * @access public
 +----------------------------------------------------------
 * @param string $str 需要转换的字符串
 * @param string $start 开始位置
 * @param string $length 截取长度
 * @param string $charset 编码格式
 * @param string $suffix 截断显示字符
 +----------------------------------------------------------
 * @return string
 +----------------------------------------------------------
 */
function msubstr($str, $start, $length, $charset="utf-8", $suffix=true)
{
    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));
    }
    return $suffix ? $slice."..." : $slice;
}
?>