ForEach does not issue an error for non-iterable non-Traversable objects

[divinity76]

Description

The following code:

<?php
declare(strict_types=1);
error_reporting(E_ALL);
\set_error_handler(function ($errno, $errstr, $errfile, $errline) {
    if (\error_reporting() & $errno) {
        throw new \ErrorException($errstr, 0, $errno, $errfile, $errline);
    }
});
$a = ["foo" => "bar"];
$o = (object)$a;
$isIterable = is_iterable($o); // false
$isTraversable = $o instanceof Traversable; // false
var_dump(["isIterable" => $isIterable, "isTraversable" => $isTraversable]);
/*
Quoting https://www.php.net/manual/en/control-structures.foreach.php
The foreach construct provides an easy way to iterate over arrays and Traversable objects.
>>>foreach will issue an error when used with a variable containing a different data type<<<
*/
foreach ($o as $key => $val) {
    var_dump(["key" => $key, "val" => $val]);
}
?>

Resulted in this output:

array(2) {
  ["isIterable"]=>
  bool(false)
  ["isTraversable"]=>
  bool(false)
}
array(2) {
  ["key"]=>
  string(3) "foo"
  ["val"]=>
  string(3) "bar"
}

But given the ForEach documentation, I expected this output instead:

array(2) {
  ["isIterable"]=>
  bool(false)
  ["isTraversable"]=>
  bool(false)
}
Fatal error: Uncaught TypeError: ForEach: Argument php/php-src#1 (iterable_expression) must be iterable or instance of Traversable

(some variant of that)

So it seems either the documentation or the implementation is wrong here.

PHP Version

PHP 8.4.5

Operating System

Ubuntu24.04

[divinity76]

Notably, if the implementation is changed to match the documentation, it would break a lot of code in the wild..

(unless we make all objects implement traversable by default, that would be a BC-compatible way of fixing it, but that would make the traversable interface pointless, I think)

[iluuu1994]

All objects are iterable by default (not in the iterator api sense, but in that foreach accepts them). This is legacy behavior and cannot easily be removed. The documentation could be clearer though. Moving this to the appropriate repository.

[divinity76]

it's not just unclear, it's wrong. if it changed to

The foreach construct provides an easy way to iterate over arrays and objects.

it would be correct. or

foreach will issue an error when used with a variable containing a different data type (except for objects)

would also be correct.
but the current wording

The foreach construct provides an easy way to iterate over arrays and Traversable objects. foreach will issue an error when used with a variable containing a different data type

is wrong.