What was wrong with ArrayHelper::index before Yii2 2.0.8?

Question

Yii

Until version 2.0.7, the documentation described the action of a function indexwith three attributes - $array, $key, $groups, although in the helper itself the entire branch of version 2 was with two - $array, $key.
So what was the matter, if only in version 2.0.8 such a simple code with three attributes was implemented? Why was there a discrepancy between the documentation and the code? Wanted to implement, but forgot?

Answer 1

This is Yii.
In general, just look at the commit history. From this commit, the third parameter appeared:
https://github.com/yiisoft/yii2/commit/ef8b0a2be0f...