Working with constants in PHP is one of the fundamental concepts that must be understood, as it is very important. Just as the name suggests, "constant" means a value that does not change during the execution of the program. In contrast to variables, which can change during the execution of the program, constants hold the same value from the time they are defined until the end of the program's execution.
Defining constants in PHP is done using the key function define. When you have a piece of data that you do not want to change during the execution, constants are the appropriate choice. This data can be examples like the site name, the version of the program, or other common values that should always remain the same.
One of the features of constants in PHP is that there is no need to prefix them with the dollar sign ($) when defining them. This makes it easier to distinguish them from variables. Additionally, constants are defined automatically as global and can be accessed from any part of the program.
Usually, constant names are written in uppercase letters to make them more distinguishable from variables. This is a standard that helps programmers write better code.
Next, we will look at an example of how to define and use constants in PHP to better familiarize ourselves with this concept and see their application in real-world projects.
Practical Example of Constant Definition in PHP
<?php
define("SITE_NAME", "mini-learn");
define("VERSION", "1.0.0");
echo "Welcome to " . SITE_NAME . ", version: " . VERSION;
?>
Line by Line Explanation of the Code
define("SITE_NAME", "mini-learn");
This defines a constant named SITE_NAME with the value "mini-learn".
define("VERSION", "1.0.0");
The constant VERSION is defined with the value "1.0.0".
echo "Welcome to " . SITE_NAME . ", version: " . VERSION;
This line uses echo to output a welcome message that includes the site name and version.