Example use of predis transactions to do check and set conditional updates. Running this example from multiple threads will maintain a consistent increment value

test.php

  // Our redis client
  $redis = $this->getContainer()->get("redis_client");

  // Set the key
  $key = 'my_key';

  // predis transaction options
  $options = array(
      'cas'   => true,    // Initialize with support for CAS operations
      'watch' => $key,    // Key that needs to be WATCHed to detect changes
      'retry' => 3,       // Number of retries on aborted transactions, after
                          // which the client bails out with an exception.
  );

  // Loop for example purposes
  while(true) {

      // try the redis transaction, it will fail if the watched key changes
      // and throw an exception.
      try {
          $responses = $redis->transaction($options, function ($tx) use ($key) {
              // get our value
              $value = $tx->get($key);
              // increment value
              $value = $value + 1;
              $tx->multi(); // With CAS, MULTI *must* be explicitly invoked.

              // set new value
              $tx->set($key, $value);
              $tx->get($key);
          });
      } catch (\Predis\Transaction\AbortedMultiExecException $e) {
          continue;
      }

      if ($responses) {
          $output->writeln($responses[1]);
      }

      usleep(500);
  }