eZContentObject::contentClassIdentifier() returns the content object's class identifier based on its numerical ID.

The class identifier is stored as a local property, but there are two issues:

• if the same transformation is requested for another object of the same class, it is fetched from the database again
• the classidentifiers_<dbname>.php cache is not used, while it has all the required data

eZContentObjectTreeNode::classIDByIdentifier() does the exact opposite and uses / handles the classidentifier cache. An easy cache, with no side effect as far as I can tell, would be to expand this method this way:

static function classIDByIdentifier( $identifier, $reverse = false )

At the end of the method, when looking for the value, this piece of code should be added before the if ( isset( $identifierHash... call:

        if ( $reverse )
        {
            $identifierHash = array_flip( $identifierHash );
        }

Then in eZContentObject::contentClassIdentifier, the DB query should be changed to a call to this method:

$classIdentifier = eZContentObjectTreeNode::classIDByIdentifier( $this->ClassID, true )