still works... with null values, too

well, this is the best solution. The only thing is now we know kyu should be related to languages ! :)

This is wrong. $yourPoint should be pushed to $classPoints in order to calculate correct average.

Edit: Ok, not necessary to pass.

Technicaly, the requirement didnt say EXPLICITLY that we could not use built-in function so there is a gray area. So despite this aproach is not "handmade from scracth" is also valid acording the kata definition.

Your code doesn't pass test
$this->assertEquals(true, betterThanAverage([2, 3], 3));

But you not included your points for the average.

Edit:
I see another comment that its the same :)

I write my code in a complicated way because I didnt know simpler function.
this is the benefit of practices, you learn what you dont know and it will be added to your experiences.

а чё всмысле

PHP is strong :)