addObjects giving a fatal error when pushing data to algolia

{
  "objectIDs": [
    "myObjectID1",
    "myObjectID2"
  ],
  "taskID": 678,
}

$index->saveObjects(array objects, [
  "autoGenerateObjectIDIfNotExist" => boolean
  // any other requestOptions
]

// add a single object
$index->saveObject(array object, [
  "autoGenerateObjectIDIfNotExist" => boolean
  // any other requestOptions
]

{
  "objectID": "myObjectID1",
  "taskID": 678,
}

$index->saveObject(
  [
    'objectID' => 'myID',
    'firstname' => 'Jimmie',
    'lastname'  => 'Barninger'
  ]
);

$objects = [/* objects */];

$res = $index->saveObjects($objects, [
  'autoGenerateObjectIDIfNotExist' => true,
  'X-Forwarded-For' => '94.228.178.246'
]);