Convert PPSX to SVG in PHP

$presentation = new Presentation("input.ppsx");
try {
    $slideCount = java_values($presentation->getSlides()->size());

    for ($slideIndex = 0; $slideIndex < $slideCount; $slideIndex++) {
        $slide = $presentation->getSlides()->get_Item($slideIndex);
        $filePath = "slide_" . ($slideIndex + 1) . ".svg";
        $outputStream = new Java("java.io.FileOutputStream", $filePath);

        try {
            $slide->writeAsSvg($outputStream);
        } finally {
            $outputStream->close();
        }
    }
} finally {
    $presentation->dispose();
}