php man page for define

DEFINE(3)								 1								 DEFINE(3)

define - Defines a named constant

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

DESCRIPTION
	Defines a named constant at runtime.

PARAMETERS
	      o $name
		- The name of the constant.

	      o $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 val-
		ues are integer, float, string or boolean values. It is possible to define resource constants, however it is not  recommended  and
		may cause unpredictable behavior.

	      o $case_insensitive
		-  If  set to TRUE, the constant will be defined case-insensitive. The default behavior is case-sensitive; i.e.  CONSTANT and Con-
		stant 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(3), constant(3), The section on Constants.

PHP Documentation Group 														 DEFINE(3)