string mb_substr ( string $str , int $start [, int $length = NULL [, string $encoding = mb_internal_encoding() ]] )-截取字符串string mb_substr ( string $str , int $start [,
string mb_substr ( string $str , int $start [, int $length = NULL [, string $encoding = mb_internal_encoding() ]] )-截取字符串string mb_substr ( string $str , int $start [,