Checking if a constant is empty

Question

Why is this not possible?

if(!empty( _MY_CONST)){
  ...

But yet this is:

$my_const = _MY_CONST;
if(!empty($my_const)){
  ...

---

define( 'QUOTA_MSG' , '' ); // There is currently no message to show

$message = QUOTA_MSG;
if(!empty($message)){
  echo $message;
}

I just wanted to make it a little cleaner by just referencing the constant itself.

Answer 1

if (!empty(constant('MY_CONST')) {
    ...
}

mixed constant ( string $name )

Return the value of the constant indicated by $name, or NULL if the constant is not defined

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

Answer 2

See the manual: empty() is a language construct, not a function.

empty() only checks variables as anything else will result in a parse error. In other words, the following will not work: empty(trim($name)).

So you'll have to use a variable - empty() is really what you want in the first place? It would return true when the constant's value is "0" for example.

Maybe you need to test for the existence of the constant using defined() instead?