OK guys, here is my solution in PHP:

function _createSupplierRelation($data){

$url = "xxx";

$db = "xxx";

$username = "xxx";

$password = "xxx";

$sku = $data[0];

$supplier_relation = $data[1];

$product_code = $data[2];

//connect

$common = ripcord::client("$url/xmlrpc/2/common");

$uid = $common->authenticate($db, $username, $password, array());

$models = ripcord::client("$url/xmlrpc/2/object");

//get odoo product id

$product = $models->execute_kw($db, $uid, $password,

'product.product', 'search_read',

array(array(array('default_code', '=', $sku)))

)[0];

//create supplier relation

$models->execute_kw($db, $uid, $password,

'product.supplierinfo', 'create',

array(array('name' => $supplier_relation, 'min_qty' => 0, 'delay' => 10, 'product_tmpl_id' => $product['id'], 'product_code' => $product_code))

);

}