How to use php defined function

php defined function is used to check whether a certain constant exists. Its syntax is defined(name). The parameter name is required and refers to the name of the constant to be checked.

#How to use php defined function?

Definition and usage

defined() function checks whether a constant exists.

Syntax

defined(name)

Parameters

name Required. Specifies the name of the constant to be checked.

Return value: TRUE if the constant exists, otherwise FALSE.

PHP Version: 4

Example

Check whether a constant exists:

<?php
define("GREETING","Hello you! How are you today?");
echo defined("GREETING");
?>

Output:

1

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