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# XVI. Character Type Functions

# Introduction

The functions provided by this extension check whether a character or string falls into a certain character class according to the current locale (see also setlocale()).

When called with an integer argument these functions behave exactly like their C counterparts from `ctype.h`.

When called with a string argument they will check every character in the string and will only return `TRUE` if every character in the string matches the requested criteria. When called with an empty string the result will always be `TRUE`.

Passing anything else but a string or integer will return `FALSE` immediately.

It should be noted that ctype functions are always preferred over regular expressions, and even to some equivalent str_* and is_* functions. This is because of the fact that ctype uses a native C library and thus processes significantly faster.

# Requirements

None besides functions from the standard C library which are always available.

# Installation

Beginning with PHP 4.2.0 these functions are enabled by default. For older versions you have to configure and compile PHP with --enable-ctype. You can disable ctype support with --disable-ctype.

The windows version of PHP has built in support for this extension. You do not need to load any additional extension in order to use these functions.

> Note: Builtin support for ctype is available with PHP 4.3.0.

# Runtime Configuration

This extension has no configuration directives defined in `php.ini`.

# Resource Types

This extension has no resource types defined.

# Predefined Constants

This extension has no constants defined.

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