# Variable Handling Functions

## Introduction

For information on how variables behave, see the Variables entry in the Language Reference section of the manual.

## Requirements

No external libraries are needed to build this extension.

## Installation

There is no installation needed to use these functions; they are part of the PHP core.

## Runtime Configuration

The behaviour of these functions is affected by settings in php.ini.

Variables Configuration Options
Name | Default | Changeable | Changelog
--- | --- | --- | ---
unserialize_callback_func | NULL | PHP_INI_ALL | Available since PHP 4.2.0.

For further details and definitions of the PHP_INI_* constants, see the php.ini directives.

Here's a short explanation of the configuration directives.

`unserialize_callback_func` string

  The unserialize() callback function will called (with the undefined class' name as parameter), if the unserializer finds an undefined class which should be instanciated. A warning appears if the specified function is not defined, or if the function doesn't include/implement the missing class. So only set this entry, if you really want to implement such a callback-function.

  See also unserialize().

## Resource Types

This extension has no resource types defined.

## Predefined Constants

This extension has no constants defined.

## Table of Contents

- debug_zval_dump — Dumps a string representation of an internal zend value to output
- doubleval — Alias of floatval
- empty — Determine whether a variable is empty
- floatval — Get float value of a variable
- get_defined_vars — Returns an array of all defined variables
- get_resource_type — Returns the resource type
- gettype — Get the type of a variable
- import_request_variables — Import GET/POST/Cookie variables into the global scope
- intval — Get the integer value of a variable
- is_array — Finds whether a variable is an array
- is_binary — Finds whether a variable is a native binary string
- is_bool — Finds out whether a variable is a boolean
- is_buffer — Finds whether a variable is a native unicode or binary string
- is_callable — Verify that the contents of a variable can be called as a function
- is_double — Alias of is_float
- is_float — Finds whether the type of a variable is float
- is_int — Find whether the type of a variable is integer
- is_integer — Alias of is_int
- is_long — Alias of is_int
- is_null — Finds whether a variable is NULL
- is_numeric — Finds whether a variable is a number or a numeric string
- is_object — Finds whether a variable is an object
- is_real — Alias of is_float
- is_resource — Finds whether a variable is a resource
- is_scalar — Finds whether a variable is a scalar
- is_string — Find whether the type of a variable is string
- is_unicode — Finds whether a variable is a unicode string
- isset — Determine whether a variable is set
- print_r — Prints human-readable information about a variable
- serialize — Generates a storable representation of a value
- settype — Set the type of a variable
- strval — Get string value of a variable
- unserialize — Creates a PHP value from a stored representation
- unset — Unset a given variable
- var_dump — Dumps information about a variable
- var_export — Outputs or returns a parsable string representation of a variable