PHP/MySQL Error

class MySQL {
      public $host;
      public $username;
      public $password;
      private $ref;
      public function mysql() {
      }
      public function connect($host, $username, $password) {
          $this->ref = @mysql_connect($host, $username, $password);
          $this->host = $host;
          $this->username = $username;
          $this->password = $password;
          if ($this->ref == false)
              return false;
          else
              return true;
      }
      public function escape($string) {
          $this->checkConnection();
          return @mysql_real_escape_string($string, $this->ref);
      }
      public function getError() {
          $this->checkConnection();
          return mysql_error($this->ref);
      }
      public function selectDB($db) {
          $this->checkConnection();
          $newRes = @mysql_select_db($db, $this->ref);
          if ($newRes == true)
              return true;
          else
              return false;
      }
      public function query($query) {
          $this->checkConnection();
          return @mysql_query($query, $this->ref);
      }
      public function getRows($query) {
          $this->checkConnection();
          $result = $this->query($query);
          return @mysql_num_rows($result);
      }
      public function returnArray($query) {
          $this->checkConnection();
          $result = $this->query($query);

          if (@mysql_num_rows($result) != 0) {
              $arr = array();
              while ($row = @mysql_fetch_assoc($result))
                  $arr[] = $row;
              return $arr;
          } else
              return array();
      }
      public function checkConnection() {
          @$this->connect($this->host, $this->username, $this->password);
      }
      public function disconnect(){
          return @mysql_close($this->ref);
      }
      public function __destruct(){
          $this->disconnect();
          sleep(4);
      }
  }