PHP iterable to array or Traversable

Question

I'm quite happy that PHP 7.1 introduced the iterable pseudo-type.

Now while this is great when just looping over a parameter of this type, it is unclear to me what to do when you need to pass it to PHP functions that accept just an array or just a Traversable. For instance, if you want to do an array_diff, and your iterable is a Traversable, you will get an array. Conversely, if you call a function that takes an Iterator, you will get an error if the iterable is an array.

Is there something like iterable_to_array (NOT: iterator_to_array) and iterable_to_traversable?

I'm looking for a solution that avoids conditionals in my functions just to take care of this difference, and that does not depend on me defining my own global functions.

Using PHP 7.1

Answer 1

Not sure this is what are you searching for but this is the shortest way to do it.

$array = [];
array_push ($array, ...$iterable);

I'm not very sure why it works. Just I found your question interesting and I start fiddling with PHP

Full example:

<?php

function some_array(): iterable {
    return [1, 2, 3];
}

function some_generator(): iterable {
    yield 1;
    yield 2;
    yield 3;
}

function foo(iterable $iterable) {
    $array = [];
    array_push ($array, ...$iterable);
    var_dump($array);

}

foo(some_array());
foo(some_generator());

It would be nice if works with function array(), but because it is a language construct is a bit special. It also doesn't preserve keys in assoc arrays.

Answer 2

Is there something like iterable_to_array and iterable_to_traversable

Just add these to your project somewhere, they don't take up a lot of space and give you the exact APIs you asked for.

function iterable_to_array(iterable $it): array {
    if (is_array($it)) return $it;
    $ret = [];
    array_push($ret, ...$it);
    return $ret;
}

function iterable_to_traversable(iterable $it): Traversable {
    yield from $it;
}

Answer 3

For php >= 7.4 this works pretty well out of the box:

$array = array(...$iterable);

See https://3v4l.org/L3JNH

Edit: Works only as long the iterable doesn't contain string keys

Answer 4

Can be done like this:

$array = $iterable instanceof \Traversable ? iterator_to_array($iterable) : (array)$iterable;