title: Class 'MongoId' not found in Laradock application
body: <p>Using Laradock (basically a set og Docker images for Laravel development), I keep getting <code>Class 'MongoId' not found</code> FatalThrowableError errors when calling <code>new \MongoId( $id )</code> in PHP.</p>
  
  <p>This post <a href="https://stackoverflow.com/questions/21953352/class-mongoid-not-found-zend-framework-with-mongodb-doctrine">Class &#39;MongoId&#39; not found (Zend Framework with MongoDB Doctrine)</a> suggests that the reason for given error is that the PHP Mongo extension isn't enabled.</p>
  
  <p>However, if I look at the <code>phpinfo()</code> output, I can see mongodb section. Doesn't that mean it's enabled?</p>
  
  <p>What else could possibly cause this error?</p>