Question Redis PHP extension and Igbinary

[Patashoow]

Server operating system version

Ubuntu 24.04

Plesk version and microupdate number

18.0.77

Hello,

I'm trying to use Igbinary as the serializer for Redis PHP extension but it seems that the Redis extension is handled in a particular way by Plesk.

I had a fresh new server and wanted to install Redis PHP extension. I went then to "Tools & Settings > PHP settings" and saw that it was already listed. As I prefer to use Igbinary as the serializer and as Igbinary wasn't isntalled, I wanted to uninstall Redis extension to reinstall it and compile it with Igbinary. When I tried to do so, Plesk said:

The PHP extension 'redis' cannot be installed or uninstalled because it is provided by Plesk out of the box, or uses packages provided by the OS vendor, or uses some other packages. You can only enable or disable the extension.

I decided then to do it through CLI. I first installed Igbinary via Plesk GUI then uninstalled Redis extension and purged everything related to it:

sudo /opt/plesk/php/8.3/bin/pecl uninstall redis
sudo apt purge plesk-php83-redis

When I reinstalled Redis extension, I compiled it with Igbinary and everything went well.
It was correctly listed on Plesk interface.
I checked through CLI /opt/plesk/php/8.3/bin/php --ri redis and it said igbinary => yes and that Igbinary was available as a serializer.

Note that when I did it, the server still didn't have any subscription yet nor any domain on it. No PHP pool existed at the time I reinstalled Redis extension.

After that, I migrated my websites with Plesk Migrator and everything went well.
Once the migration was done, I checked again to see if Redis extension was still correctly set and found that Igbinary was no longer listed in the available serializers. Only "php" and "json" were there.

So is it possible to use Igbinary with Redis PHP extension on a Plesk server or is it just a limitation that cannot be bypassed?

Thanks in advance for any help you could provide.