What are the ways to define a constant in PHP?

by

PHP constants are name or identifier that can’t be changed during execution of the script. PHP constants are defined in two ways:

  • Using define() function
  • Using const() function

In PHP, there are two primary ways to define constants:

  1. Using the define() function: This function allows you to define a constant with a specified name and value. Here’s the syntax:
    php
    define("CONSTANT_NAME", "constant_value");

    For example:

    php
    define("PI", 3.14);
  2. Using the const keyword: From PHP 5.3 onwards, you can also use the const keyword to define constants within classes or in the global scope. Constants defined using const are case-sensitive.
    php
    const CONSTANT_NAME = "constant_value";

    For example:

    php
    const PI = 3.14;

Both methods have their use cases, but const is often preferred when defining class constants for its scoping capabilities and syntactic cleanliness. However, define() is still useful for defining global constants and for scenarios where you need to dynamically define constants using expressions or variables.