SchemaDB is described as 'Powerful PHP Database Abstraction Layer' and is an app in the Development category. There are four alternatives to SchemaDB for Self-Hosted solutions. The best alternative is RedBeanPHP, which is both free and Open Source. Other great apps like SchemaDB are Propel ORM (Free, Open Source), Pork.dbObject (Free, Open Source) and PHP ActiveRecord (Free, Open Source).
Propel is an open-source Object-Relational Mapping (ORM) for SQL-Databases in PHP 5.5. Additionaly, it provides a query-builder, database schema migration, reverse engineering of existing database and much more.
It's an Object-Relation mapper for PHP 5 that attempts to be easy, fast, lightweight, uses optimized database queries and provides an easy Find() function very loosely based on rails'. Also, it has an automatic database analyzer and code generator.
PHP ActiveRecord is an open source ORM library based on the ActiveRecord pattern. It aims to massively simplify the interactions with your database and eliminate the chore of hand written SQL for common operations.