How to pull all products from all sections by a specific property in bitrix?

Question

1C-Bitrix

I broke my head and decided to write all the same here.
There is an infoblock "catalog" with goods that are divided into categories. Each product has an additional property BRAND.
Question:
How to display the entire list of brands with the quantity of goods with this brand /
Example
adidas (234) , nike(23)

Answer 1

CIBlockElement::GetList , pass an array of the following form in the grouping argument arGroupBy:

array(
'PROPERTY_BRAND' // Где BRAND это код свойсва "БРЕНД"
)