Input string specifies the input type.
"G" for GET, "P" for POST, "C" for COOKIE, "S" for string, "L" for list, and
"I" for the whole list (will return array).
If type is omitted, it returns the last input type processed.
반환값
The character encoding name, as per the type.
If mb_http_input() does not process specified
HTTP input, it returns FALSE.