One of the hardest problems to solve when developing an ORM of any complexity is in deciding how to handle the retrieval of rows that satisfy a many-to-many relationship, also known as a M:N relationship. [...] To model M:N relationships, database developers must get creative. By employing the use of a "3rd party", and by utilizing foreign keys that model a 1:N relationship, database developers can model a M:N relationship.
He looks at the Zend_Db_Table_Row class of the framework and how it works with these junction tables and how it has an issue where it returns the junction table columns too. A fix was released (in 1.10.2) for the framework to work correctly. Unfortunately, this also left those using the method out in the cold. So, Ralph has created his own workaround called a composite rowset. He includes an example snippet to give you an idea of how it works, but you can download the code from his github repository for a closer look.