php控制字符串每隔多少个字符加个换行 [ 2.0 版本 ]

public static function chunkSplit($string, $length, $end, $once = false){
//$string = iconv('gb2312', 'utf-8//ignore', $string);

    $array = array();
    $strlen = mb_strlen($string);
    while($strlen){
        $array[] = mb_substr($string, 0, $length, "utf-8");
        if($once)
            return $array[0] . $end;
        $string = mb_substr($string, $length, $strlen, "utf-8");
        $strlen = mb_strlen($string);
    }
    return implode($end, $array);
}