How to tell if a param was passed assuming it was a constant?

Question

I am using this code (note: HELLO_WORLD was NEVER defined!):

function my_function($Foo) {
    //...
}

my_function(HELLO_WORLD);

HELLO_WORLD might be defined, it might not. I want to know if it was passed and if HELLO_WORLD was passed assuming it was as constant. I don't care about the value of HELLO_WORLD.

Something like this:

function my_function($Foo) {
    if (was_passed_as_constant($Foo)) {
        //Do something...
    }
}

How can I tell if a parameter was passed assuming it was a constant or just variable?

I know it's not great programming, but it's what I'd like to do.

Edited to indicate that `HELLO_WORLD` was NEVER defined in my example, meaning all of the answers that suggest using `defined()` are useless unless I'm missing something. — Jared, Aug 13 '13 at 05:09
I have asked similar question, that may help u : http://stackoverflow.com/questions/12174971/create-an-array-of-all-constant-of-a-class — xkeshav, Aug 13 '13 at 05:09
This is helping : http://stackoverflow.com/questions/956401/can-i-get-consts-defined-on-a-php-class — xkeshav, Aug 13 '13 at 05:09

score 1 · Accepted Answer · answered Aug 13 '13 at 05:07

if a constant isn't defined, PHP will treat it as String ("HELLO_WORLD" in this case) (and throw a Notice into your Log-files).

You could do a check as follows:

function my_function($foo) {
    if ($foo != 'HELLO_WORLD') {
        //Do something...
    }
}

but sadly, this code has two big problems:

you need to know the name of the constant that gets passed
the constand musn't contain it's own name

A better solution would be to pass the constant-name instead of the constant itself:

function my_function($const) {
    if (defined($const)) {
        $foo = constant($const);
        //Do something...
    }
}

for this, the only thing you have to change is to pass the name of a constant instead of the constant itself. the good thing: this will also prevent the notice thrown in your original code.

Your first sentence is the most helpful. I've noticed that undefined constants were converted to strings before, but didn't consider it when asking the question. I think I might just have to think of an alternative way of doing what I want. — Jared, Aug 13 '13 at 05:11

Mike · Answer 2 · 2013-08-13T05:16:13.250

0

You could do it like this:

function my_function($Foo) {
    if (defined($Foo)) {
        // Was passed as a constant
        // Do this to get the value:
        $value = constant($Foo);
    }
    else {
        // Was passed as a variable
        $value = $Foo;
    }
}

However you would need to quote the string to call the function:

my_function("CONSTANT_NAME");

Also, this will only work if there is no variable whose value is the same as a defined constant name:

define("FRUIT", "watermelon");
$object = "FRUIT";
my_function($object); // will execute the passed as a constant part

edited Aug 13 '13 at 05:16

answered Aug 13 '13 at 05:03

Mike

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He wants to know whether a given param is a constant or a variable – Mr. Alien Aug 13 '13 at 05:04
Ah, I just thought he wanted to know whether it was defined or not. – Mike Aug 13 '13 at 05:06
@Mr.Alien you are correct. I've updated my question to use better wording. – Jared Aug 13 '13 at 05:09

Sutandiono · Answer 3 · 2013-08-13T05:22:11.250

0

Try this:

$my_function ('HELLO_WORLD');

function my_function ($foo)
{
   $constant_list = get_defined_constants(true);
   if (array_key_exists ($foo, $constant_list['user']))
   {
      print "{$foo} is a constant.";
   }
   else
   {
      print "{$foo} is not a constant.";
   }
}

edited Aug 13 '13 at 05:22

answered Aug 13 '13 at 05:07

Sutandiono

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How to tell if a param was passed assuming it was a constant?

3 Answers3