refactored function and variable names, and replaced variables in inner scope

src/Repository/PlaceRepository.php

@@ -29,11 +29,11 @@ class PlaceRepository
     }
 
     //TODO: use Map and User instead of id
-    public function getRandomNPlaces(int $mapId, int $n, int $userId = null): array
+    public function getRandomNPlaces(int $mapId, int $n, ?int $userId): array
     {
-        if(!isset($userId)) {
+        if(!isset($userId)) { // anonymous single player or multiplayer game
             return $this->getRandomNForMapWithValidPano($mapId, $n);
-        } else {
+        } else { // authorized user
             $unvisitedPlaces = $this->getRandomUnvisitedNForMapWithValidPano($mapId, $n, $userId);
             $oldPlaces = $this->getRandomOldNForMapWithValidPano($mapId, $n - count($unvisitedPlaces), $userId);
             return array_merge($unvisitedPlaces, $oldPlaces);
@@ -149,7 +149,7 @@ class PlaceRepository
         // set order by datetime, oldest first
         $selectOldPlaces->orderBy('last_time');
 
-        // selection algorithm with preference (weighting) for older places
+        // selection algorithm with preference (weighting) for older places using Box-Muller transform
         $pickGaussianRandomInt = function($numberOfPlaces) {
             $stdev = 0.2;
             $avg = 0.0;