Character type checking
- Introduction
 - Installing/Configuring
 - Predefined Constants
 - Ctype Functions
- ctype_alnum — Check for alphanumeric character(s)
 - ctype_alpha — Check for alphabetic character(s)
 - ctype_cntrl — Check for control character(s)
 - ctype_digit — Check for numeric character(s)
 - ctype_graph — Check for any printable character(s) except space
 - ctype_lower — Check for lowercase character(s)
 - ctype_print — Check for printable character(s)
 - ctype_punct — Check for any printable character which is not whitespace or an alphanumeric character
 - ctype_space — Check for whitespace character(s)
 - ctype_upper — Check for uppercase character(s)
 - ctype_xdigit — Check for character(s) representing a hexadecimal digit