话不多说直接上代码

private function chrNext(&$a)
    {
        $strList = preg_split("//u", $a, -1, PREG_SPLIT_NO_EMPTY);
        if ($strList[count($strList) - 1] == 'Z') {
            $str = '';
            foreach ($strList as $key => $value) {
                if ($key != count($strList) - 1)
                    $str .= $value;
            }
            if ($str == '') {
                $str = chr(ord('A') - 1);
            }
            $str = $this->chrNext($str) . 'A';
        } else {
            $strList[count($strList) - 1] = chr(ord($strList[count($strList) - 1]) + 1);
            $str = implode('', $strList);
        }
        $a = $str;
        return $a;
    }