Returning value for Propel getConnection is PDO (https://github.com/propelorm/Propel/blob/1.6/runtime/lib/Propel.php#L542-L551)
<service id="suggestions.database.handler" class="PDO" lazy="true">
<factory class="Propel" method="getConnection" />
<argument type="constant">SuggesterBundle\Model\SuggestionPeer::DATABASE_NAME</argument>
</service>
PDO prepare is