In PHP an unchangeable or constant value can be created by using a basic PHP class. That constant will be different than a normal variable because it does not initialize with “$” sign.

NOTE: The class defined constant value must be a constant expression and must not be a variable.

Initialization of a class constant is described below.

Syntax for a class constant

<?php
    // creating class with class constant
    class classConstant
    {
        const CONS = "value here...";
    }
    
    // accessing constant
    echo classConstant::CONS;
?>

After a class is defined, it may be used where ever needed in the code. To access a class and use it's constants, properties and methods a prototype has to be created that refers to that class. That is done with a keyword new. To access methods a new class prototype must use -> sign. The example below shows how to properly do it:

Example of creating and using a class constant

 

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