Proposal to improve consistency of is_iterable() and isIterable Reflection class method with what foreach actually expects

[stalkonr]

What I did?

Basically I have json_decode object, which contains key value configuration (which comes from API), like this

  $var = [
	  'key1' => 'value1',
	  'key2' => 'value2',
	  'key3' => 'value3'
  ];
  
  $object = json_decode(json_encode($var));

and I want to iterate over those key values with foreach:

foreach ($object as $key => $value) {
	echo $key;
}

which works fine. However, I want to guard this foreach from iterating on improper values. That's why I used is_iterable() (https://www.php.net/manual/en/function.is-iterable.php), In PHP RFC: Iterable (https://wiki.php.net/rfc/iterable) we can read:

It is common for a function to accept or return either an array or an object implementing Traversable to be used with foreach. However, because array is a primitive type and Traversable is an interface, there currently is no way to use a type declaration on a parameter or return type to indicate that the value is iterable.

What I wanted to happen?

I wanted that is_iterable would guard my foreach from every wrong value, like false, null and would allow object like above. See example:

  $var = [
	  'key1' => 'value1',
	  'key2' => 'value2',
	  'key3' => 'value3'
  ];
  
  $object = json_decode(json_encode($var));
  
  if (is_iterable($object) {
    foreach ($object as $key => $value) {
	echo $key;
    }
  }

What actually happened?

It turned that above object passed to is_iterable() returns false, which suprise me because it can be perfectlly fined passed to foreach, which has this warning if you pass something expected:

foreach() argument must be of type array|object, %s given

My setup

This happens on PHP 7.3, 8.1 and 8.2 (those that I tested on). I'm using Ubuntu 20.04

Summary

My PR propose to fix this inconsistency (or at least in my opinion it's inconsistency).

Please take a look and let me know what do you think, thanks!

Here is bug reported that I made: php/doc-en#2378

Best regards,
stalkonr