PHP Basics Tutorial – Constants in PHP

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Learn what constants are in PHP and how to define them using the define() function. This guide covers constant usage, syntax, and case sensitivity with examples.

What is a Constant?

A constant is a value that cannot be changed once set, unlike variables.
Constants are defined using define().

Example #1:

<?php
define("SITE_NAME", "My Awesome Site");
echo SITE_NAME;  // Output: My Awesome Site
?>

Example #2: Defines a named constant

<!DOCTYPE html>
<html lang="en">
    <head>
        <title>PHP - Contants</title>
    </head>
    <body>
        <?php
        // define(name, value, case-insensitive)
        // case-insensitive: Specifies whether the constant name should be case-insensitive. Default is false
        define("GREETING", "Welcome to Department of CS & IT!");

        function myTest() {
            echo GREETING;
        }
        myTest();
        ?> 
    </body>
</html>