PSWebServiceLibrary - Webservice - Adding product simple (without combination) there are stock problem

[Faina]

I use PSWebServiceLibrary to have a "dialog" with Prestashop.
If I add a product with this simple code:
 

xmlResponse = $webService->get(['url' => PS_SHOP_PATH."/api/products?schema=blank"]);
$fieldsXML = $xmlResponse->product[0];
$fieldsXML->state = "1";
$fieldsXML->name = "test";
$fieldsXML->price = "10.00"; 
try {
    $addResponse = $webService->add([ 'resource' => "products", 'postXml' => $xmlResponse->asXML() ]);
    $fieldsXML = $addResponse->product[0];
    echo 'Enjoy-> Your product Id is: '.$fieldsXML->id;
} 
catch (PrestaShopWebserviceException $e) { 
    echo "No good -> ".$e->getMessage(); 
}

I have my new product in catalog->products... but I haven't my new product in catalog->stocks.
When I go to catalog->stocks, my console show an error like this:
TypeError: Cannot read property 'split' of null (stock.bundle.js?1.7.6.3:7)

I have seen that the PS has create in Dbase a row in table `product_attribute` associated at new product (instead of there isn't row in tables like `product_attribute`, `product_attribute_combination`, `product_attribute_image`, ecc)
** If I delete it (by phpMyAdmin), than all work fine and the product will be visible in stocks **

If I create the product by dashboard all work fine and if I check table `product_attribute` there isn't correctly the product

I have searched many solution, like change attributes values in the insert, change them in a second time... nothing.

[Faina]

I have solved... and I think that is a bug of Prestashop or PSWebServiceLibrary
With my original code I get ALL ATTRIBUTE of the product blank shema 

$xmlResponse = $webService->get(['url' => PS_SHOP_PATH."/api/products?schema=blank"]);
$fieldsXML = $xmlResponse->product[0];

I edit only some attribute 

$fieldsXML->state = "1";
$fieldsXML->name = "test";
$fieldsXML->price = "10.00"; 
$fieldsXML->advanced_stock_management=true;
$fieldsXML->low_stock_alert=false;
$fieldsXML->minimal_quantity = "1"; 
$fieldsXML->available_for_order = true;
$fieldsXML->active = true; 

I send my new xml (attribute edited and other attribute received) to Prestashop.

$webService->add([ 'resource' => "products", 'postXml' => $xmlResponse->asXML() ]);

The problem is in the result that I have from get([...]);
The tag inside $fieldsXML have a format like (for example) <weight/> and not <weight></weight> 
So, when I edit the attribute the format will be "correct" (<state>1</state>) the other remain <attribute/>... this will be a problem when inserting the product because it seems that it's not "completely accepted" by Prestashop.

To solve the problem I have to edit each attribute as empty and then edit that I need.
This is my working code:

$xmlResponse = $webService->get(['url' => PS_SHOP_PATH."/api/products?schema=blank"]);
$fieldsXML = $xmlResponse->product[0];
foreach ($fieldsXML as $nodeKey => $node){
    $fieldsXML->$nodeKey = "";
}
$fieldsXML->state = "1";
$fieldsXML->name = "test";
$fieldsXML->price = "10.00"; 
$fieldsXML->advanced_stock_management=true;
$fieldsXML->low_stock_alert=false;
$fieldsXML->minimal_quantity = "1"; 
$fieldsXML->available_for_order = true;
$fieldsXML->active = true; 
try {
    $addResponse = $webService->add([ 'resource' => "products", 'postXml' => $xmlResponse->asXML() ]);
    $fieldsXML = $addResponse->product[0];
    echo 'Enjoy-> Your product Id is: '.$fieldsXML->id;
} 
catch (PrestaShopWebserviceException $e) { 
    echo "No good -> ".$e->getMessage(); 
}

I hope that I have explained well and that it is helpful for everyone... because there aren't many info on web.