Constants in php

A constant is an identifier for a simple value. The value cannot change during the execution of the script. A constant is case-sensitive by default.

The name of a constant follows the same rules –

1. A valid constant name starts with a letter or underscore.
2. Constants are automatically global across the entire script.

Create constant –

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

Syntax –

            define(name, value, case-insensitive – true or false);

           

Parameters:

• name: Specifies the name of the constant
• value: Specifies the value of the constant
• case-insensitive: Specifies whether the constant name should be case-insensitive. Default is false.

Example 1 - The example below create a constant valid or invalid constant name

<?php

     // Valid constant name

     define("Cyber",     "It’s cyber science."); 

     // Invalid constant name

     define("2Cyber",    " It’s cyber science.");

     // This is valid, but should be avoided

     define("__Cyber__", "Welcome in cyber science."); 

?>

Constants are Global

Constants are automatically global across the entire script.

Example – In this example use a constant inside a function, even if it is outside the function.

<?php

     define("Cyber", "Welcome to www.cyberteak.com");

     function myFun()

     {

         echo Cyber;

     }

     myFun();

?>