How to make a selection on a map with QuadKey?

Question

PHP

You need to do clustering on the label server from the map. I'm trying to do as described here https://habr.com/en/post/268621/.
Quadkeys with zoom 23 are generated in the database and stored in the decimal system


Yandex returns when zooming and when moving around the map the parameters - bbox=55.5587,36.9141,56.0537,38.4961&zoom=7
I find the middle of them

public function map()
{
$bbox = explode(',', $_GET['bbox']);
$zoom = $_GET['zoom'];
$lat = $bbox[0] + ($bbox[2] - $bbox[0]) / 2;
$long = $bbox[1] + ($bbox[3] - $bbox[1]) / 2;
//и quadkey этих данных
$quad_key = TileSystem::latLongToQuadKeyDec($lat, $long, $zoom);
$this->getClusters($quad_key, $zoom);
}

public function getClusters( $quad_key, $zoom)
  {
    $q1 = $quad_key . str_repeat("0", TileSystem::MaxZoom - $zoom);
    $q2 = $quad_key . str_repeat("3", TileSystem::MaxZoom - $zoom);
    $mask = $q1;
    $mask_plus = 1;
    $mask = $quad_key . str_repeat("3", $mask_plus);
    $mask = $mask . str_repeat("0", TileSystem::MaxZoom - $zoom - $mask_plus);

    $q1 = TileSystem::quadKey4ToDec( $q1);
    $q2 = TileSystem::quadKey4ToDec( $q2);
    $mask = TileSystem::quadKey4ToDec( $mask);

     return $this-> findBetweenQuadKeys( $q1, $q2, $mask);
  }

 public function findBetweenQuadKeys( $quad_key_l, $quad_key_r, $mask)
  {
    $entities = [];

    $sql = "SELECT `quadkey`, MIN(id) AS id, COUNT(id) AS count, AVG(longitude) AS longitude, AVG(latitude) AS latitude ";
    $sql .= "FROM `table ` ";
    $sql .= "WHERE `quadkey` BETWEEN $quad_key_l AND $quad_key_r ";
    $sql .= "GROUP BY (`quadkey` & $mask) ";

    if( $stmt =  $this->_connection->query( $sql))
    {
      foreach( $stmt as $row)
        $entities[] = $this->_createEntityFromRow( $row);
    }

    return $entities;
  }

empty returns
strange
at coordinates
$lat = 55.8935;
$long = 37.7268;
quadkey = 26919729059300 //when zoom = 23
quadkey = 6267 //when zoom = 7