Constants

Name: Constants
Rating: 5 (1 reviews)
Author: ilyas-shezad

Hi, in this tutorial i will be showing you how to use Constants.

What is a constant?
If you have ever used actionscript before, you would know that the variables are case sensitive and also dont need anything before them (like a $ identifier used for vars in php). A constant is the alternative to a php variable.

How to define a constant
The function used to define a constant is...

PHP Code

<?
define('CONSTANTNAME', 'Constant value', true);
//parameters are...
// name, value and case_insensitive
?>

The name of the constant must be put in '' so that the name is defined properley. The constant value can be anything, even a variable and it is optional to set the case_insensitive parameter. The default value for the case_insensitive parameter is false (case sensitive), this can easily be changed by setting the parameter to true.

How to use constants

Constants can be used exactly like variables...

PHP Code

<?
$debug= $_GET['debug']; //not gunna bother processing
define('DEBUG', $debug, true);
 
echo constant('DEBUG'); //echos the constant
//you can also use...
echo DEBUG; //same thing as using constant function
 
if (DEBUG == "no"){
echo "debugging is off";
}elseif (DEBUG == "yes"){
echo "debugging is on";
}
?>

How would i change the constants value?
Be creative. Use variables? if not you can always use something like...

PHP Code

<?
define('THE_TIME', time()); //time constant
${THE_TIME} = time()+3600; //changes the time
//but now if you want to echo the constant...
echo ${THE_TIME};
?>

How do i check if a constant is defined?

To check whether or not a constant is deinfed you will need to use the php defined() function...

PHP Code

<?
if (defined('CONSTANT_NAME'){
//it exists
}else{
//it doesnt exist
}
?>

Anyway i hope you enjoyed this tutorial and learnt something :P
Thanks!

Author:

ilyas-shezad

Views:

2,249

Rating:

Posted on Thursday 17^th July 2008 at 12:15 AM

darklight19
darklight19's Avatar

At least it's copy & pasta proof. :D

Posted on Wednesday 16^th July 2008 at 06:27 PM

ilyas-shezad
ilyas-shezad's Avatar

Just noticed an error in the last pice of php code provided. I missed out a close bracket in my statement.