pDB is a collection of PHP classes that implement a file based embeddable SQL database engine.
It was written in pure PHP and does not require any special extension or external resource. So, it can be distributed with any plain PHP application.
It works by storing the database tables in files that contain arrays serialized by PHP to store the data of the rows and columns of the tables. The database table files can be moved between different environments and operating systems.
It provides a SQL 92 compliant interface to execute queries like with any SQL database engine.
With small databases it can be faster than MySQL or PostgreSQL. It does not impose the overhead of establishing local socket or TCP/IP connections.