Syntax of define in PHP
bool define(string name, mixed value[, int case_insensitive])
Defines a constant named name and sets its value to value. If case_insensitive is set and is true, the operation fails if a constant with the same name, compared case insensitively, is previously defined. Otherwise, the check for existing constants is done case sensitively. Returns true if the constant could be created, or false if a constant with the given name already exists
Example of define in PHP
<?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"
?>