Define Function in PHP

In this article, we will discuss what is defined () function in PHP. The define function is one of the PHP. To define a constant, we have to use the define() function, and to retrieve the value of a constant, we have to simply specify its name.

syntax:

define(name, value, case-insensitive)

where:

• name: specifies the constant name
• value: specifies the constant value
• case-insensitive : Default value is false. It means it is case-sensitive by default.

Ex1:

<?php
define("MESSAGE", "Hello PHP User");
echo MESSAGE;
?>

Output:
Hello PHP user

Ex2:

<?php
define("MESSAGE", "Hello PHP User", true); //not case sensitive
echo MESSAGE;
echo message;
?>

Output:
Hello PHP User Hello PHP User

Ex3:

<?php
define("MESSAGE", "Hello PHP ", false); //case sensitive
echo MESSAGE;
echo message;
?>

Output:
Hello PHP
ERROR Notice : Use of undefined constant message assumed ‘message’.