How does PHP 'foreach' actually work?

Question

Let me prefix this by saying that I know what foreach is, does and how to use it. This question concerns how it works under the bonnet, and I don\'t want any an

Answer 1

As per the documentation provided by PHP manual.

On each iteration, the value of the current element is assigned to $v and the internal
array pointer is advanced by one (so on the next iteration, you'll be looking at the next element).

So as per your first example:

$array = ['foo'=>1];
foreach($array as $k=>&$v)
{
   $array['bar']=2;
   echo($v);
}

$array have only single element, so as per the foreach execution, 1 assign to $v and it don't have any other element to move pointer

But in your second example:

$array = ['foo'=>1, 'bar'=>2];
foreach($array as $k=>&$v)
{
   $array['baz']=3;
   echo($v);
}

$array have two element, so now $array evaluate the zero indices and move the pointer by one. For first iteration of loop, added $array['baz']=3; as pass by reference.