mysql - Use a PHP Variable on SELECT DateTime Between -

public function storereserva2($fechaini) {      $stmt1 = $this->conn->prepare("select count (*) reserva ? between fechaini , fechafin");      $stmt1->bind_param("s", $fechaini);      $result1 = $stmt1->execute();      $stmt1->close();      echo $result1;      print $result1;      if ($result1 === null) {           $uuid = uniqid('', true);           $stmt = $this->conn->prepare("insert reserva(unique_id, fechaini, fechafin) values(?, ? , ? + interval 2 hour)");           $stmt->bind_param("sss", $uuid, $fechaini, $fechaini);           $result = $stmt->execute();           $stmt->close();          // revisa si se hizo la reserva con su id unica          if ($result) {                  $stmt = $this->conn->prepare("select * reserva unique_id = ?");                  $stmt->bind_param("s", $uuid);                  $stmt->execute();                  $reserva = $stmt->get_result()->fetch_assoc();                  $stmt->close();                  return $reserva;              }          } else {              $reserva = $result1;              return $reserva;          }     } 

it return me

fatal error: call member function bind_param()

please want compare $fechaini variable if between fechaini , fechafin rows in table reserva.