thephpleague / fractal

                $includeObjects = $this->createIncludeObjects($includeObject);

                foreach ($includeObjects as $object) {

                    $includeType = $object['type'];

                    $includeId = $object['id'];

                    $cacheKey = "$includeType:$includeId";

                    if (!array_key_exists($cacheKey, $linkedIds)) {

                        $serializedData[] = $object;

                        $linkedIds[$cacheKey] = $object;

                    }

                }

            }

        }

        foreach ($data as $value) {

            foreach ($value as $includeObject) {

                if (isset($includeObject['included'])) {

                    foreach ($includeObject['included'] as $object) {

                        $includeType = $object['type'];

                        $includeId = $object['id'];

                        $cacheKey = "$includeType:$includeId";

                        if (!array_key_exists($cacheKey, $linkedIds)) {

                            $includedData[] = $object;

                            $linkedIds[$cacheKey] = $object;

                        }

                    }

                }

            }

        }