PHPNG (next generation) is the branch for the next php release (PHP 7). There are a few steps for firebird extension (ibase) in order to work with the new engine : You can clone the repository and test the new branch from git.
The extension changelog is here.
(There are a few patches already submitted by Dmitry Stogov)
ps: pdo_firebird seems already supported and is in the list of extensions already converted