Q:

Iterable objects and array type hinting?

I have a lot of functions that either have type hinting for arrays or use is_array() to check the array-ness of a variable. 
Now I'm starting to use objects that are iterable. They implement Iterator or IteratorAggregate. Will these be accepted as arrays if they pass through type hinting, or undergo is_array()? 
If I have to modify my code, is there a generic sort of is_iterable(), or must I do something like:
if ( is_array($var) OR $var instance_of Iterable OR $var instanceof IteratorAggregate ) { ... }

What other iterable interfaces are out there?

A:

I think you mean instanceof Iterator, PHP doesn't have an Iterable interface. It does have a Traversable interface though. Iterator and IteratorAggregate both extend Traversable (and AFAIK they are the only ones to do so).
But no, objects implementing Traversable won't pass the is_array() check, nor there is a built-in is_iterable() function. A check you could use is 
function is_iterable($var) {
    return (is_array($var) || $var instanceof Traversable);
}

To be clear, all php objects can be iterated with foreach, but only some of them implement Traversable. The presented is_iterable function will therefore not detect all things that foreach can handle.

A:

PHP 7.1.0 has introduced the iterable pseudo-type and the is_iterable() function, which is specially designed for such a purpose:

This […] proposes a new iterable pseudo-type. This type is analogous to callable, accepting multiple types instead of one single type.
iterable accepts any array or object implementing Traversable. Both of these types are iterable using foreach and can be used with yield from within a generator.

function foo(iterable $iterable) {
    foreach ($iterable as $value) {
        // ...
    }
}

This […] also adds a function is_iterable() that returns a boolean: true if a value is iterable and will be accepted by the iterable pseudo-type, false for other values. 

var_dump(is_iterable([1, 2, 3])); // bool(true)
var_dump(is_iterable(new ArrayIterator([1, 2, 3]))); // bool(true)
var_dump(is_iterable((function () { yield 1; })())); // bool(true)
var_dump(is_iterable(1)); // bool(false)
var_dump(is_iterable(new stdClass())); // bool(false)

A:

I actually had to add a check for stdClass, as instances of stdClass do work in foreach loops, but stdClass does not implement Traversable:
function is_iterable($var) {
    return (is_array($var) || $var instanceof Traversable || $var instanceof stdClass);
}

