Constants Vs. Variables for Config Files?

[Jessica]

Is there any reason to use constants over variables when creating a config-type file?
For instance, I have a file which gets included on every page, which contains paths, settings, etc.
Is there any good reason they should be constants rather than variables? The only thing I can see is that "the scope of a constant is global", meaning if I want to use it in a function I don't have to use global $var;

Your thoughts? Which is better? Does one save time somehow, etc?

[rantsh]

Not only that the "Scope" of the constant is global, the constant is [duh!] constant!!!... so there's no chance you re-write it, besides it'll help you separate stuff, say constants for configuration and variables for operations and stuff...

[corbin]

I use variables for config things, but I never knew constants were global, nor had I thought about it... I think I might start using constants now lol...

[utexas_pjm]

Try this:

[code]
<?php

define('FOO', 'bar');
$foo = 'bar';


function someThirdPartyCode_BAD()
{
global $foo;

$foo = 'not-bar';

if($foo == 'bar'){
print "Program Works <br />";
}else{
print "Obscure Bug <br />";
}
}

function someThirdPartyCode_NOT_AS_BAD()
{
define('FOO', 'not-bar');

if(FOO == 'bar'){
print "Program Works <br />";
}else{
print "Obscure Bug <br />";
}
}

someThirdPartyCode_BAD();
someThirdPartyCode_NOT_AS_BAD();

?>

[/code]

I typically create a constants.php file and store all my constant definitions there.

Best,

Patrick

[toplay]

You all said it already. As utexas_pjm code demonstrates, you can't change a constant once it has been defined (PHP will give a notice when the second define is attempted).

Global scope and not being able to change the value of a constant are the best advantages for their use. Using constants for filenames, paths and such is good because outside hacking attempts can't change their contents/value.

[Jessica]

Makes sense, good points guys! Thanks!

[rantsh]

but in that code... the constant FOO and the var $foo are 2 different things, actually if you have 2 vars $foO and $Foo, PHP treats them differently... am I wrong?

[toplay]

[quote author=rantsh link=topic=124774.msg517660#msg517660 date=1170210755]
but in that code... the constant FOO and the var $foo are 2 different things, actually if you have 2 vars $foO and $Foo, PHP treats them differently... am I wrong?
[/quote]
You are correct. However, the code example has defined 'FOO' constant at the beginning and attempts to define it again within someThirdPartyCode_NOT_AS_BAD() function, and that was what I was referring to (about PHP giving a notice on the second define attempt).

[pocobueno1388]

rantsh - Variables are case sensitive, so yes...PHP would treat those differently.

[rantsh]

HAHAHAHA!!!! I DID NOT SCROLL DOWN!!!! LOL!!!!!  :D :D :D :D ;D ;D ;D ;D

[Jessica]

Textpad rocks. Find in Files, Replace in all, and in less than a minute I fixed all my configuration to use Constants. :D

It makes a lot more sense now. Thanks :)

[toplay]

[quote author=rantsh link=topic=124774.msg517674#msg517674 date=1170211435]
HAHAHAHA!!!! I DID NOT SCROLL DOWN!!!! LOL!!!!!  :D :D :D :D ;D ;D ;D ;D
[/quote]
LOL - It happens to the best of us.

[pocobueno1388]

Amen.