PHP constant() Function

The constant() function returns the value of a constant. It also works with class constants. 

Syntax:

constant(constant)

Parameter Values:

• constant: It is a required value that specifies the value of the constant.

Return Value: It returns the value of a constant if the constant is defined else returns NULL.

Note: It works on PHP 4.0 or newer versions.

Exceptions: If the constant is not defined, it throws an E_WARNING error. It gives a run time warning without script termination.

The following are the PHP programs to show the working of the constant() function.

Example 1: Case sensitive

PHP

<?php

// Define a constant
define("Home","Welcome to GeeksforGeeks");

echo constant("Home");
?>

Output:

Welcome to GeeksforGeeks

Example 2:  Case insensitive

PHP

<?php

// Define a case insensitive constant
define("GFGConstant","True denotes case-insensitive", true);

echo constant("gfgconstant");
?>

Output: 

True denotes case-insensitive

Reference: https://www.php.net/manual/en/function.constant.php