[development] += on arrays
larry at garfieldtech.com
Wed Jan 18 02:42:21 UTC 2006
On Tuesday 17 January 2006 20:28, Jeremy Epstein wrote:
> First of all, you should remember this fundamental difference between
> array_merge() and the array + operator:
> " Don't forget that numeric keys will be renumbered! ... If you want
> to completely preserve the arrays and just want to append them to each
> other, use the + operator."
> (from http://www.php.net/manual/en/function.array-merge.php)
> Personally, I find that the re-indexing behaviour of array_merge() is
> often not what I want, so I'm finding that I use the + operator more
> and more.
> Also, consider these two examples:
> $array1 = array_merge($array1, $array2);
> $array1 += $array2;
> In the first example (assuming that the keys aren't numeric), $array2
> is guaranteed to have all its values preserved; in the second example
> (no matter what type the keys are), $array1 is guaranteed this. So...
> On 1/18/06, Larry Garfield <larry at garfieldtech.com> wrote:
> > So... array_merge($a, $b) favors $a, while $a += $b favors $b? Wouldn't
> > that mean that
> > array_merge($a, $b) == $b += $a
> It's the other way around, Larry. :-) But the two operations are only
> equivalent IF there are no numeric keys! If there are, then
> array_merge() behaves differently (and stupidly, IMO).
Ah ha. So I was backward but had the right idea. :-) The direction I'm going
> On a related note: perhaps we should agree on a recommended way (i.e.
> one of the above two ways) of merging arrays in Drupal? I'd like to
> see the + operator encouraged, as it's more predictable, and
> (according to chx) is also faster. But I don't know that we can outlaw
> array_merge() altogether (as we did with array_key_exists() recently)
> as there may still be times when it's needed, since it is a bit
> different to the + operator.
Exactly. If array_merge($a, $b) == $b += $a iff $a and $b are strictly
associative arrays, and += is substantially faster, and Drupal uses
associative arrays a LOT, it seems like this is a good language-level
optimization to make and recommend.
Larry Garfield AIM: LOLG42
larry at garfieldtech.com ICQ: 6817012
"If nature has made any one thing less susceptible than all others of
exclusive property, it is the action of the thinking power called an idea,
which an individual may exclusively possess as long as he keeps it to
himself; but the moment it is divulged, it forces itself into the possession
of every one, and the receiver cannot dispossess himself of it." -- Thomas
More information about the development