I'm triing to install a fresh new Debian 9.8 with imscp 1.5.3-2018120800 with PHP 7.1 by default, and then installed phpswitcher. And when trying to add support to php 5.6 ("perl php_compiler.pl --auto-setup 5.6"), it says that the Bison 3.0 is not supported with php 5.6, so there is no way to add php 5.6. (https://bugs.php.net/bug.php?id=69055)
I have others servers with imscp, and the only thing that it's different is that we added PHP 5.6 by default on imscp (and not 7.1), and I think that then the bison version installed is 2.x.
So I checked the documentation on php and says that php 7 supports bison > 2.4 (https://secure.php.net/manual/en/install.unix.php)
- PHP 5.6: >= 2.4, < 3.0
- PHP 7.0 - 7.3: 2.4 or later (including Bison 3.x)
- PHP 7.4: > 3.0
So I think that maybe the version installed by default can be the bison 2.x in order to have compatibility with php 5.6 ¿?
The only solution is to add php 5.6 by default on imscp Nuxwin ?