mongodb\Collection createIndex()

Column name or list of column names. If array is given, each element in the array has as key the field name, and as value either 1 for ascending sort, or -1 for descending sort. You can specify field using native numeric key with the field name as a value, in this case ascending sort will be used. For example:

[
    'name',
    'status' => -1,
]

List of options in format: optionName => optionValue.

Whether the operation successful.

on failure.