How to make a uniform selection from an array?

Question

PHP

Good day!
Unable to create an algorithm. There is an array with a certain number of elements. It is necessary to distribute ALL elements of the array into groups, according to N elements, and so that the categories are distributed evenly.

$arr = Array(
  "Категория 1" => Array(
    "Товар 1",
    "Товар 2",
    "Товар 3",
    ...
    "Товар 30",
  ),
  "Категория 2" => Array(
    "Товар 1",
    "Товар 2",
    "Товар 3",
    ...
    "Товар 20",
  ),
  "Категория 3" => Array(
    "Товар 1",
    "Товар 2",
    "Товар 3",
    ...
    "Товар 10",
  ),
);

Those. if I wanted to make a selection from the $arr array, then it would return 10 times 6 elements each, where 3 products are from Category 1, 2 products are from Category 2 and 1 product is from Category 3. Can you tell me in which direction to move?