PHP. Руководство по PHP. 2005
ctype_alnum
ctype_alnum
Описание
bool ctype_alnum (string text)Checks if all of the characters in the provided string, text, are alphanumeric. In the standard C locale letters are just [A-Za-z] and the function is equivalent to preg_match('/^[a-z0-9]*$/i', $text).