Google\Cloud\Datastore\Operation::lookup PHP Method

    public function lookup(array $keys, array $options = [])
    {
        $options += ['className' => null, 'sort' => false];
        $this->validateBatch($keys, Key::class, function ($key) {
            if ($key->state() !== Key::STATE_NAMED) {
                throw new InvalidArgumentException(sprintf('Given $key is in an invalid state. Can only lookup records when given a complete key. ' . 'Given path was %s', (string) $key));
            }
        });
        $res = $this->connection->lookup($options + $this->readOptions($options) + ['projectId' => $this->projectId, 'keys' => $keys]);
        $result = [];
        if (isset($res['found'])) {
            $result['found'] = $this->mapEntityResult($res['found'], $options['className']);
            if ($options['sort']) {
                $result['found'] = $this->sortEntities($result['found'], $keys);
            }
        }
        if (isset($res['missing'])) {
            $result['missing'] = [];
            foreach ($res['missing'] as $missing) {
                $key = $this->key($missing['entity']['key']['path'], $missing['entity']['key']['partitionId']);
                $result['missing'][] = $key;
            }
        }
        if (isset($res['deferred'])) {
            $result['deferred'] = [];
            foreach ($res['deferred'] as $deferred) {
                $key = $this->key($deferred['path'], $deferred['partitionId']);
                $result['deferred'][] = $key;
            }
        }
        return $result;
    }

 /**
  * Get multiple entities inside a transaction
  *
  * Example:
  * ```
  * $keys = [
  *     $datastore->key('Person', 'Bob'),
  *     $datastore->key('Person', 'John')
  * ];
  *
  * $entities = $transaction->lookup($keys);
  *
  * foreach ($entities['found'] as $entity) {
  *     echo $entity['firstName'];
  * }
  * ```
  *
  * @param Key[] $key The identifiers to look up.
  * @param array $options [optional] {
  *     Configuration Options
  *
  *     @type string|array $className If a string, the name of the class to return results as.
  *           Must be a subclass of {@see Google\Cloud\Datastore\Entity}.
  *           If not set, {@see Google\Cloud\Datastore\Entity} will be used.
  *           If an array is given, it must be an associative array, where
  *           the key is a Kind and the value is the name of a subclass of
  *           {@see Google\Cloud\Datastore\Entity}.
  * }
  * @return array Returns an array with keys [`found`, `missing`, and `deferred`].
  *         Members of `found` will be instance of
  *         {@see Google\Cloud\Datastore\Entity}. Members of `missing` and
  *         `deferred` will be instance of {@see Google\Cloud\Datastore\Key}.
  */
 public function lookupBatch(array $keys, array $options = [])
 {
     return $this->operation->lookup($keys, $options + ['transaction' => $this->transactionId]);
 }