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svnpenn

> PHP really got this one right (and immediately messed it up by mixing it with arrays, but hey, PHP).

No, it didnt. What PHP calls "array" is actually an Ordered Map, as you alluded to:

https://yaml.org/type/omap

it literally says that in the documentation, paragraph one, sentence one:

> An array in PHP is actually an ordered map.

https://php.net/types.array

The issue, if one exists, is that PHP doesnt have a sequence type:

https://yaml.org/type/seq

but one is provided as a package:

https://php.net/class.ds-sequence

https://github.com/php-ds/extension

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Sure, PHP arrays are actually ordered maps, but it's super confusing when used as arrays. I mean, look at code like this:

    $arr = [];
    $arr[2] = "two";
    $arr[0] = "zero";
    $arr[1] = "one";
    echo join($arr, ", ");
    // two, zero, one

In any other language, the result of similar code would be "zero, one, two". You'd need to `ksort` this thing to get it to behave like a normal bog-standard boring array.

Everybody's writing PHP code pretending that it has arrays when really, it does not. The gotchas are way bigger than the gotchas in Python <3.7's unordered maps. It's a mess.

I disagree. The behavior you exhibit makes more sense than the behavior you imagine.

You start with an _empty_ array, then (somehow) set the third element of that array? That makes very little sense.

Had you _initialized_ your example as an array with a length of 3, your desired behavior would, indeed, manifest.

The problem is PHP calling an ordered map an array. Array in pretty much every other language means a sequence indexed by integers.

Ideally the maintainers of PHP would rename it and deprecate the use of `array()` over a long period of time.

The PHP documentation refers to them as "associative arrays", which is technically correct, but I agree I'm not sure how they could have conflated these concepts so badly.

I believe the "associative array" terminology came from Perl. Though Perl's associative arrays don't have any guaranteed order. And Perl also has normal arrays.

In that situation, Matlab allocates an array of length 3, fills it with “empty” values (depending on the type), and then sets the third element to the value. That’s what I’d have expected to happen here too...

Would you expect it to do that if somebody wrote the following?

    $id = 12835151;
    $arr[$id] = Get_thing_with_id( $id );

yes.

In my bog standard PHP I would do $thing = Get_thing_with_id( $id ); if(!empty($thing)){process($thing);}

If $arr were an array I would, though I'd cringe at the wasted space (unless it were a sparse array).

Obviously, I'd agree that a map/associative array/dict/etc is a better choice here; I'm just annoyed about the name.

>You start with an _empty_ array, then (somehow) set the third element of that array? That makes very little sense.

Well, there's no reason a language could not initialize an empty array to some initial capacity, either on declaration or when you add an indexed element.

I have to disagree also.

The order inserted makes most sense in most cases. Hand crafting integer based array indexes out of order is rare. And as you say a simple ksort call guarantees sort order.

    ksort($arr);
    echo join($arr, ", ");
    // one, two, three

Exactly. Of you hand craft an array you probably need it in that order.

Then why not put it in order while you're hand crafting it?

I literally just learned "bog-standard" 10 minutes ago and now I see it here. And no, don't Baader-Meinhof me, I would have noticed this weird term in random text in the past.

>I would have noticed this weird term in random text in the past.

Well, no so weird, I'm not a native english speaker, and I've seen the term hundreds of times over the years...

It's also quite common on HN:

https://www.google.com/search?q=site%3Anews.ycombinator.com+...

Would you though? Appears at least once a week: https://hn.algolia.com/?dateRange=all&page=0&prefix=false&qu...

Baader-Meinhof denial!

Baader-Meinhof Dunning-Kruger?

I'm aware of the terms "bog" and "bog-standard", but not being from the UK, I'm not sure what is so standard about bogs.

Why wouldn‘t you just push/append to the end of the array with '$arr[]'? There is no need for explicit keys in PHP. The gotcha is writing code in PHP pretending you are using a different language.

So how can you access, say, the third element of your ordered map in PHP ?

    array_values($arr)[2];

I mean youd probably have to iterate. Either that or use a package with proper array support.

That's messed up

In practice, it's almost never an issue. The standard lib has push/pop/shift/pad methods available.

So example, if you had numeric indices that you wanted to guarantee that index order is equal to insertion order, you'd create an array using $my_array = array_pad([], 20, null); If it's an array that you didn't create, the ksort(...) method will order the array for you as expected.

Edit: after reading through the documentation on array_pad, it looks like it will even correct key order in existing arrays. https://www.php.net/manual/en/function.array-pad.php#87735

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