Question

On the php.net manual page for define(), there’s a user-contributed note that suggests that you can usefully call define() from within a function.

Lightly paraphrasing, the suggestion is to create a function like this:

<?php  
function xdefine($a) {
  foreach($a as $k => $v)
    define($k, $v); 
}  
?>

and then to subsequently use it like this:

<?php
xdefine(array(
    "SECOND" => 1,
    "MINUTE" => 60,
    "HOUR" => 3600,
    "DAY" => 86400,
    "WEEK" => 604800,
    "MONTH" => 2592000, // 30 days month
    "YEAR" => 31536000,
    "LEAPYEAR" => 31622400
));
?>

But both my sense and my experience are that this doesn’t work: after the xdefine() call, each of the identifiers just evaluates to its own name, not to the value that xdefine() supposedly bound to it.

The reason seems pretty obvious to me (i.e., because the symbols get their values as the module containing the call to xdefine() is being parsed/loaded), but maybe there’s some subtlety I’m missing. The author of the post named his function something different, using a cute Unicode character, but I’m pretty sure that’s just a cosmetic difference.

(BTW, something similar does work for me if I don’t define a function like xdefine(), but rather, just run the same foreach() loop over the contents of the array, provided that both the loop and the array are at module scope. This is also expected behavior, from my perspective.)

So, can someone look at the original post and tell me if there’s really anything to it? Or does the author just have it wrong?

(I’d post this to the referenced php.net page, but I think I will get more eyes on the question faster if I post it here instead 🙂

Answer 1

The sample function works. The scope of a constant is global. However, the reason(s) to do this are dubious imho.