DB class having pdo, on inheriting should not re-initiate connection

When I'm calling different models in one then multiple times db connection establishes, I want only one, is it possible. Below is piece of my mvc

class Database{
    private $db;
    private $stmt;
    function __construct()
    {
        parent::__construct();
        $root = dirname(dirname(__FILE__));
        $this->config = parse_ini_file($root . '/app/config.ini', true);

        $db = $this->config['database settings'];
        $host = $db['host'];
        $user = $db['user'];
        $pword = $db['pword'];
        $db_name = $db['db'];
        $this->db = new PDO("mysql:host=$host;dbname=$db_name", $user, $pword, array(
            PDO::MYSQL_ATTR_FOUND_ROWS => true, PDO::ATTR_PERSISTENT => true
        ));
        $this->db->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
        $this->db->setAttribute(PDO::ATTR_EMULATE_PREPARES, false);        
    }
    function executeQuery($query, $params = array())
    {
         $this->stmt = $this->db->prepare($query);
         if (! ($this->stmt)) {
           throw new Exception('Query failed while preparing');
         }
         try {
            $this->stmt->execute($params);
         } catch (PDOException $e) {
            throw $e;
         }
     }
     function getRecords($query, $params = array(), $array = false, $all = false)
     {
          $this->executeQuery($query, $params);

           $records = array();
          if ($this->totalRecords() > 0) {
             if ($array) {
                $this->stmt->setFetchMode(PDO::FETCH_ASSOC);
             } else {
                 $this->stmt->setFetchMode(PDO::FETCH_OBJ);
             }
            if ($all) {
               $records = $this->stmt->fetchAll();
            } else {
                while (($record = $this->stmt->fetch()) !== false) {
                   $records[] = $record;
               }
           }
        }
        return $records;
     }
  }

Below is the model where I use it

class TestModel extends Database{
  function __construct(){
    parent::__construct();
  }
  function getUsers(){
     return $this->getRecords("SELECT * FROM users");
  }
}

Below is another model I want to call the method getusers to use it for some purpose.

require("path_to_testmodel"); 
require("path_to_some_model");
require("path_to_some_other_model");
class TestModel2 extends Database{
    function __construct(){
       parent::__construct();
       $this->test_model = new TestModel();
       $this->some_model = new SomeModel();
       $this->some_other_model = new SomeOtherModel();
    }
    function doSomething(){
       $users = $this->test_model->getUsers();
    }
}

If I am including multiple models like TestModel() in one of the models, here seen is every time a database connection is established, sometimes I get too many connections error or in some system I get memory allocation issue.

Please help me to fix this.