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Constants in PHP

In this tutorial I will explain about constant in PHP. This topic contains following sections

   1. Software requirement

   2. Technical knowledge

   3. What do you mean by constant?

   4. Rules for making constant

   5. Syntax

   6. Example

Software requirement

Before you start reading this tutorial you should make sure that

1. XAMPP is installed on your machine.

2. Notepad (or any text editor) is installed on your machine.

Technical knowledge

In order to understand this tutorial you should know about identifiers in programming language and their purpose.

What do you mean by constant?

In computer language constant is an identifier whose value cannot be changed during the execution of the program.

Rules for making constant

In PHP a constant should always start with an alphabet or underscore (_).

Syntax

We can set the value of constant using define function. Here is the syntax

define(constant_name, constant_value,is_case_insensitive);

   1. First parameter is the name of the constant

   2. Second parameter is the value of the constant.

   3. Third one is the optional parameter which specifies if the constant name is case insensitive or not. By default the value is false which means that the constant name is case sensitive.

Example

<?php
define("PIE", "3.14", true);
echo pie
?>

This above code will display ‘3.14’

<?php
define("PIE", "3.14");
echo pie
?>

And the code above will throw an error –‘Notice: Use of undefined constant pie’ as the constant is case sensitive

Posted By -	Karan Gupta

Posted On -	Monday, September 8, 2014

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