Evitar mensaje de error en leer xml

[syntex]

Como evitar el mensaje de error en leer un archivo xml?

Warning: file_get_contents(http://xxxxxx/xml_s3/xml_serverxxxxx...output=metaxml) [function.file-get-contents]: failed to open stream: HTTP request failed! HTTP/1.1 500 Internal Server Error in C:\xampp\htdocs\ini_articulos.php on line 63

Fatal error: Uncaught exception 'Exception' with message 'String could not be parsed as XML' in C:\xampp\htdocs\ini_articulos.php:63 Stack trace: #0 C:\xampp\htdocs\ini_articulos.php(63): SimpleXMLElement->__construct('', 0, false) #1 C:\xampp\htdocs\ini_articulos.php(409): imagenes('SD-C08GJ(BL3A', 'MARCA', '43', 'MODELO') #2 {main} thrown in C:\xampp\htdocs\ini_articulos.php on line 63

Código PHP:

  $ruta_PartNumber = "http://xxxx:[email protected]/xml_s3/xml_serverxx233.cgi?prod_id=".urlencode(trim(strtolower($PartNumber))).";vendor=".urlencode(trim(strtolower($Marca))).";lang=ES;output=metaxml";            
                
                # BUSCAR IMG DEL XML DEL PROVEEDOR
                # ************************************************************************     
                $file_PartNumber = @fopen($ruta_PartNumber,"r");     
                if ($file_PartNumber)
                {
                    fclose($file_PartNumber);
                    
                    if ($sxe = new SimpleXMLElement(file_get_contents ( $ruta_PartNumber ), NULL, false))
                    {