Redis not saving data to docker container server

Question

I have the following docker compose configurations:

version: "3.9"
services:
  redis:
    image: redis:latest
    volumes:
      - redis_data:/var/redis/data
    restart: always
    environment:
      ALLOW_EMPTY_PASSWORD: "yes"
      REDIS_DISABLE_COMMANDS: "FLUSHDB,FLUSHALL"
    ports:
      - "6379:6379"
volumes:
  db_data: { }
  redis_data:
    driver: local

In my code, I have:

public function __construct()
    {
        $this -> redis = new Client([
            'scheme' => 'tcp',
            'host' => 'localhost',
            'port' => 6379
        ]);
    }

    public function connect()
    {
        $this -> redis -> connect();
        var_dump($this -> redis -> getConnection());
        $this -> redis -> set('foo', "aaa");
        echo "REDIS VALUE: " . $this -> redis -> get('foo');
    }

And my debugging result is:

object(Predis\Connection\StreamConnection)#18 (4) {
  ["resource":"Predis\Connection\AbstractConnection":private]=>
  resource(149) of type (stream)
  ["cachedId":"Predis\Connection\AbstractConnection":private]=>
  NULL
  ["parameters":protected]=>
  object(Predis\Connection\Parameters)#16 (1) {
    ["parameters"]=>
    array(3) {
      ["scheme"]=>
      string(3) "tcp"
      ["host"]=>
      string(9) "localhost"
      ["port"]=>
      int(6379)
    }
  }
  ["initCommands":protected]=>
  array(0) {
  }
}
REDIS VALUE: 

It seems to be connecting to the docker redis container, but the data is not saving. I'm not quite sure what the issue seems to be at this point.