How to get a user’s code via SESSION

Question

Hi. I was wondering if that’s possible

$nome=$_SESSION['nome'];
$codigoUsuario=buscaUsuario($nome);
inserirVenda($codigoUsuario,$codigoProduto);

I take his name via session step to a variable, I search the bank and return your code to insert it in another table in the bank. The following error is happening.

Object of class mysqli_result could not be converted to string

here is where I get the information that was sent from html.

   $nome=$_SESSION['nome'];
            $resultado2=buscaUsuario($nome);
            if($resultado2){
                while($linha = mysqli_fetch_assoc($resultado2)){
                    $codigoUsuario=$linha['codigoUsu'];
                }
            }

            inserirVenda($codigoUsuario,$codigoProduto);

Giving an error in the function insert.

function inserirVenda($codigoUsuario,$codigoProduto){
    conectar();
    query("INSERT INTO venda (codigoProduto,codigoUsuario) VALUES ($codigoProduto,$codigoUsuario)");
    fechar();

}

Fatal error: Uncaught Error: Call to Undefined Function mysql_connect_error() in C: xampp htdocs igor_work 2 connectionBD.php:22 Stack trace: #0 C: xampp htdocs igor_work 2 crudVenda.php(36): query('INSERT INTO ven...') #1 C: xampp htdocs igor_work 2 controleVenda.php(26): inserirVenda('12', 'code') #2 {main} thrown in C: xampp htdocs igor_work 2 connectionBD.php on line 22