int define(string name, mixed value, int [case_insensitive]);
Defines a named constant, which is similar to a variable except:
Constants do not have a dollar sign '$' before them;
Constants may be accessed anywhere without regard to variable scoping rules;
Constants may not be redefined or undefined once they have been set; and
Constants may only evaluate to scalar values.
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 1 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." ?>
define() returns TRUE on success and FALSE if an error occurs.