Michelangelo van Dam has a new post to his site looking at using Redis for PHP sessions storage and changes related to the use of PHP 7.1.

In case you have missed it, PHP 7.1.0 has been released recently. Now you can’t wait to upgrade your servers to the latest and greatest PHP version ever. But hold that thought a second…

With PHP 7 lots of things have changed underneath the hood. But these changed features can also put unexpected challenges on your path. [...] One of these challenges that we faced was getting PHP 7.1 to play nice storing sessions in our Redis storage. In order to store sessions in Redis, we needed to install the Redis PHP extension that not only provides PHP functions for Redis, but also installs the PHP session handler for Redis.

When he installed the extension, the latest version (redis-3.1.0), he was given an error message about a failure to read the session data. He shares a bit of code he used to try to debug and diagnose the problem (and a Docker environment) that still resulted in the error. Ultimately they narrowed it down and discovered that it was the Redis extensions causing the problems. Downgrading it from 3.1.0 to 3.0.0 solved the issue right away.