push new value to mongodb inner array - mongodb/php

Question

i have this document in mongo:

{
   \"_id\": ObjectId(\"4d0b9c7a8b012fe287547157\"),
   \"done_by\": [\"1\"]
}

and i want to add another va

Answer 1

$push => array('done_by' => '2')

So says the manual: { $push : { field : value } }