private static function makePropertyValue($name,$value,$osm){
    $oStruct = $osm->Bridge_GetStruct("com.sun.star.beans.PropertyValue");
    $oStruct->Name = $name;
    $oStruct->Value = $value;
    return $oStruct;
}

private static function word2Pdf($officeFile, $pdfFile) {
    $osm = new COM("com.sun.star.ServiceManager") or die ("Please be sure that OpenOffice.org is installed");
    $args = array(self::makePropertyValue("Hidden",true,$osm));
    $oDesktop = $osm->createInstance("com.sun.star.frame.Desktop");
    $oWriterDoc = $oDesktop->loadComponentFromURL(self::$pdfFileDirFixd.$officeFile,"_blank", 0, $args);
    $export_args = array(self::makePropertyValue("FilterName","writer_pdf_Export",$osm));
    $oWriterDoc->storeToURL(self::$pdfFileDirFixd.$pdfFile,$export_args);
    $oWriterDoc->close(true);
}