This extension is considered unmaintained and dead. However, the source code for this extension is still available within PECL GIT here: » https://github.com/php/pecl-database-interbase.
Firebird is a relational database offering many ISO SQL-2003 features that runs on Linux, Windows, and a variety of Unix platforms. Firebird offers excellent concurrency, high performance, and powerful language support for stored procedures and triggers. It has been used in production systems, under a variety of names since 1981.
InterBase is the name of the closed-source variant of this RDBMS that was developed by Embarcadero/Inprise. More information about InterBase is available at » http://www.embarcadero.com/products/interbase.
Firebird is a commercially independent project (fundation) of C++ programmers, technical advisors and supporters developing and enhancing a multi-platform relational database management system based on the source code released by Inprise Corp (now known as Embarcadero) under the InterBase Public License v.1.0 on 25 July, 2000. More information about Firebird is available at » http://www.firebirdsql.org/.
Note:
This extension has been moved to the » PECL repository and is no longer bundled with PHP as of PHP 7.4.0
This extension supports InterBase versions 6 and up and Firebird version 2.0 and up.