PHP team released long awaited 7.1.0 version bringing us:
- Nullable types
- Void return type
- Iterable pseudo-type
- Class constant visiblity modifiers
- Square bracket syntax for list() and the ability to specify keys in list()
- Catching multiple exceptions types
As usual, Yii 2.0 is well prepared and works well with PHP 7.1 so feel free to upgrade if needed.
If you wonder about thoughts behing each change, check out RFC wiki.