Variable-named Constants...possible?

Anon

It's hard to come up with a descriptive name for this question. An example is easier.

Variable variables are easy to understand (once you see them in action). If I'm expecting someone to tell me what variable to access (passed in a variable itself called $varName), I can access the specified variable like so:

$put_it_here = $$varName;

Now here's the question: is there anyway to do the same for constants? ie. I don't know the name of the constant, but some variable with the name will be passed to be. An example:

define( "FOO", 1 );
$constName = "FOO";

Now, having only $constName, is there a way to access the constant FOO? $$constName does not work (naturally, since there is no variable named FOO) so I'm at a loss. Any ideas? Solutions? Is it even possible?

lawnmowerman

Is this what you mean?

<?php

define( "FOO", 'test' );
$constName = FOO;

print 'FOO = ' . FOO . "\n";
print 'constName = ' . $constName . "\n";

-Rich

Anon

No, I'm afraid not. I guess I still haven't explained this very well 🙂 Let me try a different way.

Say an included PHP script conditionally defines several constants like so:

<?php

$type = (something done on the disk maybe)

switch( $type ) {
case 0:
define( "FOO", 0 );
$constName = "FOO";
break;
case 1:
define( "BAR", 1 );
$constName = "BAR";
break;
}

Now assume for a moment that this actually makes sense to do 🙂 Now assume I have another PHP script that includes/requires the above. And say I don't want to use something like defined() to check for the existence of each constant (maybe to make it easier to update the code in the future?). Given only the variable $constName, is there a way to get at the constant $constName specifies? ie. if I was using variables, I'd just do $$constName, but since there are constants we're talking about there's no way to do that.

Is there some sort global array like $CONSTANTS[] indexed by constant name? Something like this? Should there be?

I know this is odd behaviour, and likely pretty rare, but I have in fact run into a situation where this would extremelly helpful; without going into gorey details, it's a meta-editor of sorts (editor for an editor 🙂 where the object is to make it as flexible as possible.

lawnmowerman

Hmmm...

Not that I know of or can find...

It's a very good question though!

Sorry, I can't help any further with this, but why not use a named indexed array to store your constants?

-Rich

Anon

Yes, it would seem to be possible. I realise that it may be to late to help you, however, you should look at the new function, 'constant':

http://www.php.net/manual/en/function.constant.php

I was having the exact same problem, note this is only available in version 4.0.4.

From the description it seems very useful.

Phil