based on what I've read and then applied, you don't have to specifically create a database or table, you just initialize it. 
Indeed, files are not being written inside /data/db, but they will the first moment you start adding data.
So, I'm taking as an example Twitter, with no db defined, I'm still going to have the db available if I run this code:
<?php
define('TWITTER_API_VERSION', 1);
date_default_timezone_set("Europe/Dublin");
try 
{
    $m = new Mongo(); // connect
    $db = $m->selectDB("example");
}
catch ( MongoConnectionException $e ) 
{
    echo '<p>Couldn\'t connect to mongodb, is the "mongo" process running?</p>';
    exit();
}
$updates = file_get_contents( "http://api.twitter.com/". TWITTER_API_VERSION ."/statuses/public_timeline.json" );
$updates = json_decode( $updates );
if ( $updates && is_array( $updates ) && count( $updates ) )
{
    foreach ( $updates as $update )
    {    
        $db->users->insert( $update );
    }
}
?>
Hope this was helpful!
Good luck!
Vladimir Ghetau
 add a note
 add a note