---
title: Constants
---
## Constants
Constants are a type of variable in PHP. The `define()` function to set a constant takes three arguments - the key name, the key's value, and a Boolean (true or false) which determines whether the key's name is case-insensitive (false by default). A constant's value cannot be altered once it is set. It is used for values which rarely change (for example a database password OR api key).

### Scope
It is important to know that unlike variables, constants ALWAYS have a global scope and can be accessed from any function in the script.

### Example
```PHP
<?php
define("freeCodeCamp", "Learn to code and help nonprofits", false);
echo freeCodeCamp;
```
**Output:**
```text
Learn to code and help nonprofits
```

#### More Information:
* <a href="https://secure.php.net/manual/en/language.constants.php" rel="nofollow">php.net constants manual</a>
* <a href="https://secure.php.net/manual/en/function.define.php" rel="nofollow">php.net define() manual</a>