Up until this point, we've seen the _rev key in our CouchDB documents, but we haven't had to actually use it in our application. In order for us to take any actions on an already existing document, we'll need to pass _rev, along with _id, to ensure that we are acting on the most recent document.
Let's prepare for this by adding a $_rev variable to our base class.
1. Open
classes/base.phpin your working directory, and add the$_revvariable.abstract class Base { protected $_id; protected $_rev; protected $type;2. Unfortunately, now anytime we call the
to_jsonfunction,_revwill always be included, regardless of it being used or not. If we were to send CouchDB anull _rev, it would throw an error. So, let's add some code to theto_jsonfunction inclasses/base.phpto unset our_revvariable if it has no value set.public function to_json() { if (isset($this->_rev) === false) { unset($this->_rev); } return json_encode...