You’ve quickly put together the code to add files to MongoDB. But as any good DBA and Developer knows not everything that goes into your database should stay there.

Yes, you already figured out it’s as simple as $grid->remove(). Here is something to keep in mind. MongoGridFS::remove won’t present you with a message if it failed. To ensure that a file was successfully removed use MongoDB::lastError(). You’ll get an array in return that will show something along the lines of:

Array
(
[err] =>
[n] => 0
[ok] => 1
)

The field to watch is “ok”. The value of “1″ will return if the remove went according to plan. Otherwise you’ll get “0″ and it’s time to check the value for “err”. If you’re wondering about the “n” its the number of files that were removed.

In practice your code could look something like this:

/*
* function remove
* Removes files from Mongo and captures error if failed
* @return mixed
*/
public function remove($criteria)
{
    //Get the GridFS Object
    $grid = $db->getGridFS();

    //Setup some criteria to search for file
    $id = new MongoID($criteria['_id']);

    //Remove file
    $grid->remove(array('_id'=>$id), true);

    //Get lastError array
    $errorArray = $db->lastError();
    if ($errorArray['ok'] == 1 ) {
        $retval = true;
    }else{
        //Send back the error message
        $retval = $errorArray['err'];
    }

    return $retval;
}

With a few short lines you’re able to capture the error message and do whatever you like with it. Hopefully this helps keep your fs.files and fs.chunks collections clean.

As a quick followup to the last blog, I was asked to demonstrate how we could include some metadata with a file during or after upload.

This is a great feature since we can retrieve all the information attached with a document during a query. Including metadata (i.e. comments, dates, votes or WHATEVER ELSE YOU LIKE) is just as easy.

We are going to pick up the ball at the point where you’ve got all your MongoDB objects ready:

<?php
$date = new MongoDate();
//Use $set to add metadata to a file
$metaData = array('$set' => array(“comment”=>”MongoDB is awesome”, “date”=>$date));

//Just setting up search criteria
$criteria = array('_id' => $id);

//Update the document with the new info
$db->grid->update($criteria, $metaData);

?>

Did you break a sweat? Probably not.

BTW, I threw in a little extra tidbit there with MongoDate(). It’s a better way of inputting a date into Mongo instead of using PHP date with a bunch of formatting to get it just right.