How to insert new node after root in RSS?

Question

RSS

Hello. I am forming an RSS and I want the newly added one to be added after the channel description, and not at the end of the file, if I do the usual appendChild. I found the insertBefor method in the manual, but I can’t figure out how to attach it. Can you please tell me how to use the insert method correctly?
PS It is necessary that there be such a structure.

Answer 1

$domDocument->insertBefore($firstItem, $newItem);