mongodb customer service PHP
===

I am wondering what is the best layout for a customer service mongodb layout

I thought something like this, but not sure. So thought I would ask.

    {
    "userid":(MONGODBUSERID),
    "subject":"subjectofissue",
    "issue":"issue that the user has",
    "replies":[{
       "whoreplied":"staff/customer",
       "uid":"userid of replier",
       "msg":"msg of reply"
    }]
    }

Is that the best way to do it?
If so how would I update the replies array with PHP? cos I would need to insert into the replies array without over writing the past replies.