Como inserir usando o Casse Mysqli php

public function salvar(){
 $con = new conexao("127.0.0.1", "root", "", "Membricia");
 $con->conectar();

 $con->stmt_init();
 $stmt = $con->prepare('INSERT INTO Logon (Login, Senha) VALUES ( ?, ?);
');
 $stmt->bind_param('ss', $this->getUsuario(), $this->getSenha());
 $stmt->store_result();
 if($stmt->execute()){

 echo "Registro Salvo";
 echo "<br>";
 $stmt->close();

 }
 else {
 echo "<br>Impossivel salvar o registro<br>";
 $con->close();

 }
 }

##########################################

SO QUE NAO SALVA !!!!

###############

Aqui esta o meu bando .....

mysql> select * from Logon ; <<< ---- nome da tabela Logon ..
+----+-------+-------+
| id | Login | Senha |
+----+-------+-------+
| 1 | admin | admin |
| 2 | natan | natan |
+----+-------+-------+
2 rows in set (0.00 sec)

Obs : nao retorna nenhum erro .... mais tmb não grava ..