(mongodb >=1.17.0)
MongoDB\BSON\PackedArray::offsetGet — Returns the value of an index in the array
Returns the value associated with the given index. If the index is not present in the array, an exception is thrown.
注意: When encountering a value encoded as 64-bit integer in the BSON array, the return value of this method will be a MongoDB\BSON\Int64 instance.