Constants are like variables with fixed values and they can not be changed once defined. Constants have global scope by default.

How to create a constant

You can create constants in two ways:

1. using define()

define() is used to create a constant.

define(name, value, case-insensitive)

• name: name of the constant
• value: value of the constant
• case-insensitive: Specifies whether the constant name should be case-insensitive or not. By default it is set to false.

Example

<?php
define("MESSAGE", "Happy learning!");
echo MESSAGE;
?>

Run here

You can define the constant name as case-insensitive by making the third parameter in the above syntax to true.

<?php
define("MESSAGE", "Happy learning!\n", TRUE);
echo MESSAGE;
echo MesSAGE;
echo message;
?>

Run here

2. Using const keyword

const keyword is used to create a constant. Constants defined with const keyword are case-sensitive.

<?php
const MESSAGE = "Happy learning!";
echo MESSAGE;
?>

Run here