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I've seen a bunch of the other Mongo PHP $push questions up here on SO, but for some reason none of what they're saying is working, so I'm posting my own version.

Basically, I'm trying to follow a guideline set by 10gen where representing something like a news feed or blog/comment post should be done using buckets - making documents that hold a certain number (50) of events (comments, etc.), and then creating multiple documents as the content grows.

What I'm trying to do is push documents ($event) into an array (events), but there seems to be some confusion with PHP when the document doesn't exist (upserting). I tried to do it with an insert, but insert and $push don't play well together.

Here's what I have right now:

$historyDoc = array('_id'=>$uID, 'count'=>1,
  array('$push' => array('events' => $event)));

$query = array('_id'=>$uID);

//add user to history
$collection->update($query,$historyDoc,
    array('safe'=>true,'timeout'=>5000,'upsert'=>true));

Where $event is a properly-formatted array (document) of things (e.g. timestamp, userID, action, name) and $uID is a MongoID object taken from another collection.

The result that I get is this:

{
"_id": {
    "$oid": "4f77ec39fef97a3965000000"
    },
"0": {
    "$push": {
        "events": {
            "timestamp": 1333259321,
            "action": "achievement",
            "pts": 0,
            "name": "join"
        }
    }
},
"count": 1
}

Which is good, because my document is at least showing up right, but how the hell is there a key with a "$" in it? It's not like I'm failing to escape the $...I've been very intently using single quotes for that exact reason.

Maybe there's something I'm missing, or maybe I broke PHP, but I've been wrestling with this one for awhile and there's nothing I can thing of. It's holding my whole project up, so....>:/

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2 Answers

up vote 1 down vote

Your update document is ill-formed, try this:

$historyDoc = array('_id' => $uID, 
                    'count' => 1,
                    '$push' => array('events' => $event));
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Tried that one before. I just did it again, and here's the error message I got: exception 'MongoCursorException' with message 'Modifiers and non-modifiers cannot be mixed' in /var/fog/apps/app34260/trinker.phpfogapp.com/php/register.php:190. I saw something in the PHP Mongo Manual somewhere that looked promising, so I'm gonna try that. – borego Apr 1 '12 at 6:16
Ah, indeed, you can't mix those. Try converting count to $set. You can't $set an _id, though. – Sergio Tulentsev Apr 1 '12 at 6:19
I have a solution but stupid StackOverflow won't let me post it for another 7 hours because I don't have over 100 rep. It's times like these where the reputation system backfires. Screw you, SO. See: my edit for solution – borego Apr 1 '12 at 6:24
You can post to a comment, and I'll edit my answer :) – Sergio Tulentsev Apr 1 '12 at 6:26
up vote 1 down vote accepted

It's not the most elegant solution, but it looks like it works. Apparently there's a problem with using $push on a new document (insert or upsert) (EDIT: It might actually be the issue with combining atomic and non-atomic thing that's the problem. You can't use atomic operators on _id, so...). However, you can get around it by inserting the document first and then updating/upserting it.

In order to initialize an array in Mongo via PHP, you need to create a document with an empty array a a value, as seen here:

$historyDoc = array('_id'=>$uID.'-0',
        'count'=>1, 
        'events'=>array());

From there, you can simply take what you were going to put into the first index and upsert it later:

$collection->update($query, $historyDoc,
             array('safe'=>true,'timeout'=>5000,'upsert'=>true));

$collection->update($query,
            array('$push'=>array('events'=>$event)),
            array('safe'=>true,'timeout'=>5000,'upsert'=>true));

This yields a resulting document of the form:

{
"_id": "4f77f307fef97aed12000000-0",
"count": 1,
"events": [
    {
        "timestamp": 1333261063,
        "action": "achievement",
        "pts": 0,
        "name": "join"
    }
]
}

Source: Mongo PHP Manual - Updates

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