How toinsert purchase order from PHPXMLRPC if my odoo instance is MultiCompany, I always have this error  : 

Traceback (most recent call last):\n
      File "/home/odoo/src/odoo/16.0/odoo/addons/base/controllers/rpc.py", line 150, in xmlrpc_2\n
        response = self._xmlrpc(service)\n
      File "/home/odoo/src/custom/trial/saas_trial/controllers/main.py", line 302, in _xmlrpc\n
        res = super(OdooRPC, self)._xmlrpc(service)\n
      File "/home/odoo/src/odoo/16.0/odoo/addons/base/controllers/rpc.py", line 130, in _xmlrpc\n
        result = dispatch_rpc(service, method, params)\n
      File "/home/odoo/src/odoo/16.0/odoo/http.py", line 366, in dispatch_rpc\n
        return dispatch(method, params)\n
      File "/home/odoo/src/odoo/16.0/odoo/service/model.py", line 37, in dispatch\n
        res = execute_kw(db, uid, *params[3:])\n
      File "/home/odoo/src/odoo/16.0/odoo/service/model.py", line 59, in execute_kw\n
        return execute(db, uid, obj, method, *args, **kw or {})\n
      File "/home/odoo/src/odoo/16.0/odoo/service/model.py", line 65, in execute\n
        res = execute_cr(cr, uid, obj, method, *args, **kw)\n
      File "/home/odoo/src/odoo/16.0/odoo/service/model.py", line 50, in execute_cr\n
        result = retrying(partial(odoo.api.call_kw, recs, method, args, kw), env)\n
      File "/home/odoo/src/odoo/16.0/odoo/service/model.py", line 133, in retrying\n
        result = func()\n
      File "/home/odoo/src/odoo/16.0/odoo/api.py", line 464, in call_kw\n
        result = _call_kw_model_create(method, model, args, kwargs)\n
      File "/home/odoo/src/odoo/16.0/odoo/api.py", line 444, in _call_kw_model_create\n
        result = method(recs, *args, **kwargs)\n
      File "", line 2, in create\n
      File "/home/odoo/src/odoo/16.0/odoo/api.py", line 415, in _model_create_multi\n
        return create(self, arg)\n
      File "/home/odoo/src/odoo/16.0/addons/purchase/models/purchase.py", line 238, in create\n
        company_id = vals.get('company_id', self.default_get(['company_id'])['company_id'])\n
    AttributeError: 'list' object has no attribute 'get'\n

Here is my code using : 

"phpxmlrpc/phpxmlrpc": "^4.10"

public function createPurchaseOrderDraft($partner_id, array $orderLines, $company_id)
{

    $response = $this->getResponse();
    $uid = $response->value()->scalarval();

    $models = new \PhpXmlRpc\Client($this->odooUrl . '/xmlrpc/2/object');
    $message = new Request('execute_kw');

    // Ajout des paramètres par défaut
    $this->addDefaultParam($message, $uid, "purchase.order", "create");

    $data = [
        new Value(
            [
                new Value("company_id", "string"),
                new Value("=", "string"),
                new Value($company_id, "int"),
            ], "array"
        ),
        new Value(
            [
                new Value("partner_id", "string"),
                new Value("=", "string"),
                new Value($partner_id, "int"),
            ], "array"
        ),
        new Value(
            [
                new Value(
                    [
                        new Value("state", "string"),
                        new Value("=", "string"),
                        new Value("draft", "string"),
                    ], "array"
                ),
            ], "array"
        ),
        new Value(
            [
                new Value(
                    [
                        new Value("name", "string"),
                        new Value("=", "string"),
                        new Value("Commande d'achat", "string"),
                    ], "array"
                ),
            ], "array"
        ),

    ];
    $date = (new \DateTime())->format('Y-m-d H:i:s');
    $orderLinesData = [];
    foreach ($orderLines as $orderLine) {
        $oneLine = new Value([
            new Value(0, "int"),
            new Value(false, "boolean"),
            new Value([
                new Value([
                    new Value("name", "string"),
                    new Value("=", "string"),
                    new Value($orderLine['name'], "int"),
                ], "array"),
                //date_planned
                new Value([
                    new Value("date_planned", "string"),
                    new Value("=", "string"),
                    new Value($date, "string"),
                ], "array"),
                new Value([
                    new Value("product_id", "string"),
                    new Value("=", "string"),
                    new Value($orderLine['product_id'], "int"),
                ], "array"),
                new Value([
                    new Value("product_qty", "string"),
                    new Value("=", "string"),
                    new Value($orderLine['product_qty'], "int"),
                ], "array"),
                new Value([
                    new Value("price_unit", "string"),
                    new Value("=", "string"),
                    new Value(0, "int"),
                ], "array"),
            ], "array"),
        ], "array");
        $orderLinesData[] = $oneLine;
    }
    $data[] = new Value($orderLinesData, "array");

    // Construction des données de commande
    $args = [
        new Value(
            $data
            , "array"
        ),
    ];



    $message->addParam(new Value($args, 'array'));
    $response = $models->send($message);

Regards !