Updating Evernote note with Evernote php sdk - evernote

Question

I can get notes(real contents, not just metadata) from the evernote API. However, calling notestore->update() always gives me a EDAMUserException.
My php code is below, the arguments are self-explanatory:
//add text to note
//if append=true then the text will be appended to the end, else it will be appended to the start
public function addToNote($new_content, $access_token, $note_store, $note_guid, $append = true){
$note = $note_store->getNote($access_token, $note_guid, true, false, false, false);
$note->content +="<en-note>Note updated</en-note>";
$note_store->updateNote($access_token, $note);
}
I've already did a lot of searching before I asked here, and here are the things I know:
According to: https://dev.evernote.com/doc/articles/permissions.php it says that there are two types of api keys, one is the basic access and one is for full access, I have full access, this is proved by no exception was thrown during $note_store->getNote() call, and I did output the data from that call, I can actually get the contents of the note.
In the same page as 1: "Certain API functions are only available to official Evernote applications and services. These functions are described as such in the API Reference and will throw an EDAMUserException with the error code PERMISSION_DENIED if called by a third-party application." I read the API documentation here: https://dev.evernote.com/doc/reference/NoteStore.html#Fn_NoteStore_updateNote
It does not mention that it is blocked by default.

Answer 1

I think I figured out what was wrong. Evernote actually has its own DTD document format, if the "content" section of the note is not a valid document, then the request is denied. In my case it was not denied because my API key's access level, but because the "content" I gave was not a proper evernote format.
if I set:
$note->content='<!DOCTYPE en-note SYSTEM "http://xml.evernote.com/pub/enml2.dtd"><en-note><div>testing complete!!!</div></en-note>';
Then the note will be successfully updated.
However, for other users that are getting this exception and using the right format, it is most likely:
1.your api key does not have full access, choose the full access option while you request an api key.
2.usually you would start testing on the "sandboxed"(https://sandbox.evernote.com) version of their site, you need to register another account on the sandboxed site(you real evernote account doesn't carry over) and test with that account. If you do not do this, your account will not exist on the sandboxed account and anything you do will not work.