Can't get Redis memcache working on Ubuntu 18.04

I can’t work out how to get the Redis memcache stuff working.

OS: Ubuntu 18.04
PHP: v7.2.24-0ubuntu0.18.04.4

So, I’ve installed redis:

apt install memcached
apt-get install redis

It seems to be running fine:

service redis-server status
● redis-server.service - Advanced key-value store
   Loaded: loaded (/lib/systemd/system/redis-server.service; enabled; vendor preset: enabled)
   Active: active (running) since Thu 2020-06-11 08:19:27 UTC; 40min ago
  Process: 22021 ExecStop=/bin/kill -s TERM $MAINPID (code=exited, status=0/SUCCESS)
  Process: 22048 ExecStartPost=/bin/sh -c echo $MAINPID > /var/run/redis/ (code=exited, status=0/SUCCESS)
  Process: 22025 ExecStart=/usr/bin/redis-server /etc/redis/redis.conf (code=exited, status=0/SUCCESS)
 Main PID: 22046 (redis-server)
    Tasks: 4 (limit: 4915)
   CGroup: /system.slice/redis-server.service
           └─22046 /usr/bin/redis-server

Jun 11 08:19:27 systemd[1]: Starting Advanced key-value store...
Jun 11 08:19:27 systemd[1]: Started Advanced key-value store.

As per the docs, I’m trying to add this into /config/config.php:

   'memcache.local' => '\OC\Memcache\Redis',
  //'memcache.locking' => '\\OC\\Memcache\\Redis',
   'filelocking.enabled' => 'true',
    'redis' =>
      array (
         'host' => 'localhost',
         'port' => 6379,

Then when I try and run the admin panel, all I get is an nginx 500 IS error. i’ve tried finding the error log to tell me what the error is, but there seems to be nothing in there.

Any suggestions?