Difference between Constant and Variable in PHP

Constant in PHP

A constant in PHP is a value that cannot be changed once it is declared. It is defined using the ‘define()‘ function and their names are case sensitive.

Example:

<?php
   define("Hello", "Welcome to Webeduclick!");
   echo Hello;
?>

Output:

Welcome to Webeduclick!

Variable in PHP

A variable in PHP is a placeholder for storing data that can be changed during the execution of a script. Variables are defined using a dollar sign ($) followed by the variable name. It can store different types of data such as strings, integers, floats, arrays, objects, etc.

<?php
$a=5;
$b=10;
$c=$a+$b;
echo "$c";
?>

Output:

Difference between Constant and Variable

Constant	Variable
1. In PHP constants, there is no need to use $ sign.	1. In PHP Variables, the $ sign is been used.
2. A PHP constant once defined cannot be redefined.	2. A PHP variable can be undefined as well as can be redefined.
3. The data type of PHP constant cannot be changed during the execution of the script.	3. The data type of the PHP variable can be changed during the execution of the script.
4. PHP constants are written in numbers.	4. PHP variables are written in letters and symbols.
5. PHP constant is comparatively slower than PHP variable	5. A PHP variable is comparatively faster than the PHP constant