add products by php

[moh]

hello developpers,

 i'm trying to add products to my Prestashop via php using webservices, i called the empty xml file, i've insert the resources product but i've got error when i'm trying to send the file to my shop (i've got an eroor 400)

<?php

define('DEBUG', false);
define('PS_SHOP_PATH', 'http://myshop');
define('PS_WS_AUTH_KEY', 'UV******************4');
require_once('./PSWebServiceLibrary.php');
require_once'config_demo.php';

                      
                                        
                  try
                    {
                              $webService = new PrestaShopWebservice(PS_SHOP_PATH, PS_WS_AUTH_KEY, DEBUG);

                      }                               
                  catch (PrestaShopWebserviceException $e)
                              {  // Here we are dealing with errors
                                      $trace = $e->getTrace();
                                      if ($trace[0]['args'][0] == 404) echo 'Bad ID';
                                      else if ($trace[0]['args'][0] == 401) echo 'Bad auth key';
                                      else echo 'Other error<br />'.$e->getMessage();
                             } 

$xml = $webService->get(array('url' => 'http://myshop/api/products?schema=synopsis'));
$resources = $xml->product->children();

unset($resources->manufacturer_name);
unset($resources->quantity);
unset($resources->position_in_category);
unset($resources->associations);
unset ($resources->associations->categories->category);

$resources->id = 1992;

for($i = 0; $i < count($resources->name->language); $i++){
    $resources->name->language[$i] = 'wortisbox';
    $resources->link_rewrite->language[$i] = 'mon-produit-SAM';
}

$resources->price = 285;
//$resources->description="caisse enregistreuse de 10 pouces";
$resources->reference = "light";
echo "<pre>";
//var_dump($resources) ;
echo "</pre>";

try
    {
      $opt = array( 'resource' => 'products' );
      $opt[ 'postXml' ] = $xml->asXML();
      $xml = $webService->add($opt);
      echo "product added";
    }
catch(PrestaShopWebserviceException $e)
    {  $trace = $e->getTrace();
      if ($trace[0]['args'][0] == 404) echo 'Bad ID';
      else if ($trace[0]['args'][0] == 401) echo 'Bad auth key';
      else echo 'Other error<br />'.$e->getMessage();
            echo "failed send";
    }
                                     
?>

can you help to resolve the problem please 

thank you ^__^