What are Constants in PHP?

[NIcaBoy]

Hi friends,
I am new programmer for the PHP programming language. So I am not having enough knowledge about it. So thought that you guys would help me again. The solutions that you provide are very helpful. I am not able to get about the constants that are used in PHP. So please tell me what are the constants that are used in PHP?

[Viensterrr]

The PHP constant is very similar to a PHP variable in that it is used to store a value. The constant() function returns the value of a constant. The syntax is as follows :

constant(constant) 

If you want to run a program several times using a different value each time, you do not need to search throughout the entire program and change the value at each instance.

[MELTRONICS]

The constant parameter is used for specifying the name of the constant to check. The following example may help you :

<?php
define("Wish","Hi! How are you today?");

echo constant("Wish");
?>

[CodGuru]

You can also make use of the valid and invalid constant names, just like I have used in following example :

<?php

define("Demo",     "something");
define("Demo1",    "something else");
define("Demo2", "something more");

define("Demo3",    "something");

define("Demo4", "something"); 

?>

[void]

You can also retrieve the value of a constant dynamically. The following example demonstrates the same :

<?php

define('Demo','It works!');
define('Demo1','It works again!');

$changing_variable = 'bar';
echo constant('Demo2' . strtoupper($changing_variable));

$changing_variable = 'Demo3';
echo constant('Demo3' . strtoupper($changing_variable));

?>