How to output unlimited nesting of elements in an array through PHP?

Question

PHP

Actually. There is a JSON pulled through the VK API with all the user's messages. This JSON is decoded and the result is a multidimensional array. In this array, each specific array is one message. In the message, in addition to the text, there may be a forwarded message. In a forwarded message, messages that are still being forwarded (i.e., the nesting is actually infinite). And each message (both regular and forwarded) can have an attachment (or multiple attachments).
For example:
To access attachments in a normal message, you would use:
$arr[message_number]["attachments"][attachment_number_in_message][attachment_type][element_with_link_to_attachment]
For attachments in a forwarded message:
$arr[message_number]["fwd_messages"][forwarded_message_number]["attachments"][attachment_number_in_message][attachment_type][element_with_link_to_attachment]
If anything -- https://vk.com/dev/message.
You should get HTML with a hierarchical structure (a block with a message, inside of which is a block with a forwarded message, and inside this block there is another one; in each such block there is an image). In general, the representation that messages have on the site itself.
The problem is how to handle it all. If levels 1 or 2 - everything is simple. But if there can be an infinite number of these levels, this is already a problem.
How to implement this, given the possible unlimited nesting?

Answer 1

The problem is how to handle it all.

Not certainly in that way. You now have a problem with the formalization of the task, which should come out in the end.
Smoke towards graphs and breadth first search.

Answer 2

this is the working js code on the topic:

var fwdfun = function (fwds,level=1) {
  try {
  for(var i in fwds){
    const fwd = fwds[i];
    var qo = ">".repeat(level);
     console.log(qo+fwd.num);
  if(fwd.arr){
     fwdfun(fwd.arr,level + 1);
  }
  }
}catch(error){
  console.error(error);
}
}

fwdfun(obj);