Returns TRUE if every
character in text is a
letter from the current locale,
FALSE otherwise. In the standard C locale letters are just
[A-Za-z] and ctype_alpha() is
equivalent to (ctype_upper($text) ||
ctype_lower($text)), but other languages have letters
that are considered neither upper nor lower case.
See also ctype_upper(),
ctype_lower(), and
setlocale().