Question

When I create an mapped-superclass inheritance between 2 entities and do a yaml doctrine2 export the extends property is not set in the derived table

Answer 1

This is correct behaviour. Mapped superclass is php-class only inheritance which can't be described by YML/XML format.

Please check Doctrine2 documentation for more information: http://docs.doctrine-project.org/projects/doctrine-orm/en/latest/reference/inheritance-mapping.html