PHP Constants

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What is a PHP constant?

PHP constants are names or identifiers that cannot be changed during script execution

Constants are similar to the variable, except that, once defined, they can never be undefined or modified. These remain constant throughout the program.

Constants does not need $ in front.
But, as a convention of PHP programmers, constants are written in capital letters (A-Z) for easier observation.

To create a constant, use the define() function.

Syntax:

Where:
name: Specifies the name of the constant
value: Specifies the value of the constant
case-insensitive:

to create a constant with a case-sensitive name:

<?php
define("MESSAGES", "Welcome to agernic.com, have a nice day.");

  echo MESSAGES;
?>
        

Create a constant with a case-insensitive name:

<?php
define("MESSAGES", "Welcome to agernic.com, have a nice day.", true);

  echo messages;
?>  

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In PHP7, we can create an Array constant using function define().

<?php

define("colors", [

"red",

"green",

"blue"

]);

echo colors[2];

?>
      

PHP constants are automatically global and can be used throughout the script.

<?php
define("MESSAGES", "Welcome to agernic.com, have a nice day.");

  function my_Test() {

  echo MESSAGES;

  }

  

  my_Test();

  ?>