constant
defined
Misc. Functions
PHP Manual

# define

(PHP 4, PHP 5)

define — Defines a named constant

### Description

bool define ( string `$name` , mixed `$value` [, bool `$case_insensitive` = false ] )

Defines a named constant at runtime.

### Parameters

`name`

  The name of the constant.

`value`

  The value of the constant; only scalar and null values are allowed. As of PHP 7 it also possible to use array value. Scalar values are integer, float, string or boolean values. It is possible to define resource constants, however it is not recommended and may cause unpredictable behavior.

`case_insensitive`

  If set to `TRUE`, the constant will be defined case-insensitive. The default behavior is case-sensitive; i.e. CONSTANT and Constant represent different values.

  > Note:

  > Case-insensitive constants are stored as lower-case.

### Return Values

Returns `TRUE` on success or `FALSE` on failure.

### Changelog

Version | Description
--- | ---
7.0.0 | array values are allowed.

### Examples

Example #1 Defining Constants

`<?php
define("CONSTANT", "Hello world.");
echo CONSTANT; // outputs "Hello world."
echo Constant; // outputs "Constant" and issues a notice.
define("GREETING", "Hello you.", true);
echo GREETING; // outputs "Hello you."
echo Greeting; // outputs "Hello you."
// Works as of PHP 7
define('ANIMALS', array(
'dog',
'cat',
'bird'
));
echo ANIMALS[1]; // outputs "cat"
?>`

### See Also

- defined() - Checks whether a given named constant exists
- constant() - Returns the value of a constant
- The section on Constants

constant
defined
Misc. Functions
PHP Manual