How to use $sample with geo near in mongodb with PHP

I am trying to run a query that allows to find nearby users given a certain maximum distance. I would like that after finding them, it would randomly take 10 documents among those found and I don’t know how to do it.
i tried using $sample but i got several misuse errors. how should i do?

code:

$result = ["coordinate"=> [
     '$near'=> [
       '$geometry'=> [
          "type"=> "Point" ,
          "coordinates" => [ 12.099700 , 45.267670 ]
       ],
       '$maxDistance'=> 40000
     ]
   ]];

thanks!