QuaaxTM 0.8.0 by Johannes Schmidt.
From the webpage:
QuaaxTM is a PHP ISO/IEC 13250 Topic Maps engine which implements PHPTMAPI. This enables developers to work against a standardized API. QuaaxTM uses MySQL with InnoDB or MariaDB with XtraDB as storage engine and benefits from transaction support and referential integrity.
From the news:
0.8.0 passes all unit tests on MariaDB 5.5.35 using XtraDB storage engine. Prior versions of MariaDB should also work but are not tested.
If you don’t know MariaDB, https://mariadb.org/.