MySqli为值返回NULL，无法插入或选择

My problem is that my db have no errors and still ignore my inserts, selects etc. So i tried var_dump() and it gives NULL for all variables. That is my connection query:

 $this->conexao = new mysqli('localhost:3307','root','', 'construsite');

And this is wrong, i think:

 public 'conexao' => 
 object(mysqli)[2]
  public 'affected_rows' => null
  public 'client_info' => null
  public 'client_version' => null
  public 'connect_errno' => null
  public 'connect_error' => null
  public 'errno' => null
  public 'error' => null
  public 'error_list' => null
  public 'field_count' => null
  public 'host_info' => null
  public 'info' => null
  public 'insert_id' => null
  public 'server_info' => null
  public 'server_version' => null
  public 'stat' => null
  public 'sqlstate' => null
  public 'protocol_version' => null
  public 'thread_id' => null
  public 'warning_count' => null

and my function to insert that is ignored:

public function registro(){
    //comando sql para inserir novo cliente
    $comando = "INSERT INTO clientes(id, nome_cliente, email_cliente, telefone_cliente, senha_cliente, data_nasc_cliente) "
    . "VALUES (NULL, '$this->nome_cliente', '$this->email_cliente', '$this->telefone_cliente', '$this->senha_cliente', STR_TO_DATE( '$this->data_nasc_cliente', '%Y/%d/%m')";
    //executa o comando
    $registro_resultado = $this->conexao->query($comando); //executa o comando
    return $registro_resultado;
}

I tried to find in google and here but i could not. (Sorry my bad english!!)

Id is primary key, and primary key doesn't accept null. if your primary key auto increment so remove id from insert query.

$comando = "INSERT INTO clientes(nome_cliente, email_cliente, telefone_cliente, senha_cliente, data_nasc_cliente) "
    . "VALUES ('$this->nome_cliente', '$this->email_cliente', '$this->telefone_cliente', '$this->senha_cliente', STR_TO_DATE( '$this->data_nasc_cliente', '%Y/%d/%m'))";