Convert PPTM to BMP in PHP

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

    for ($slideIndex = 0; $slideIndex < $slideCount; $slideIndex++) {
        $slide = $presentation->getSlides()->get_Item($slideIndex);
        $slideImage = $slide->getImage(2.0, 2.0);

        try {
            $filePath = "slide_" . ($slideIndex + 1) . ".bmp";
            $slideImage->save($filePath, ImageFormat::Bmp);
        } finally {
            $slideImage->dispose();
        }
    }
} finally {
    $presentation->dispose();
}