The name of the constant is given by name;
the value is given by value.
The optional third parameter
case_insensitive is also available. If the
value TRUE is given, then the constant will be
defined case-insensitive. The default behaviour is
case-sensitive; i.e. CONSTANT and Constant represent different
values.
Example 1. Defining Constants
<?php define("CONSTANT", "Hello world."); echo CONSTANT; // outputs "Hello world." echo Constant; // outputs "Constant" and issues a notice.