//get merchant data with its id

public function getUserData($id){

    $stmt = $this->conn->prepare("SELECT * FROM seller WHERE id= ? LIMIT 1");
    $stmt->bind_param("i", $ud);
    $stmt->execute();
    $result = $stmt->get_result();

    if($result){
        $seller = $result->fetch_assoc();
        $stmt->close();
        return $seller;
    }
    else{
        return NULL;
    }
}