function substr_cut($user_name){
            $strlen= mb_strlen($user_name, 'utf-8');
            $firstStr= mb_substr($user_name, 0, 1, 'utf-8');
            $lastStr= mb_substr($user_name, -1, 1, 'utf-8');
            return $strlen== 2 ? $firstStr . str_repeat('*', mb_strlen($user_name, 'utf-8') - 1) : $firstStr . str_repeat("*", $strlen - 2) . $lastStr;
        }

        /*
        普通截取
        */
        function hide_name($name, $sep = '*')
        {
            $len = strlen($name);
            $str = '';
            for ($i = 0; $i < $len; $i++) {
                $str .= ($i == 0 || $i == $len - 1) ? $name{$i} : $sep;
            }
            return $str;
        }