app.php

class MyController
{

  private $client;

  public function __construct(Client $client)
  {
    $this->client = $client;
  }

  public function doSomeQueries()
  {
    // Query DB 1
    $result = $this->client->run('MATCH (n) RETURN count(n)', null, null, 'server1'); 
    // Query DB 2
    $result2 = $this->client->run('MATCH (n) RETURN count(n)', null, null, 'server2'); 
}