$writer->End();
// save changes to the current page
$doc->PagePushBack($page);
// Set the default viewing preference to display 'Layer' tab.
$prefs = $doc->GetViewPrefs();
$prefs->SetPageMode(PDFDocViewPrefs::e_UseOC);
$doc->Save($output_path . "pdf_layers.pdf", SDFDoc::e_linearized);
echo nl2br("Done.\n");
// The following is a code snippet shows how to selectively render
// and export PDF layers.
$doc = new PDFDoc($output_path . "pdf_layers.pdf");
$doc->InitSecurityHandler();
if (!$doc->HasOC()) {
echo nl2br("The document does not contain 'Optional Content'\n");
} else {
$init_cfg = $doc->GetOCGConfig();
$ctx = new Context($init_cfg);
$pdfdraw = new PDFDraw();
$pdfdraw->SetImageSize(1000, 1000);
$pdfdraw->SetOCGContext($ctx);
// Render the page using the given OCG context.
$page = $doc->GetPage(1);
// Get the first page in the document.
$pdfdraw->Export($page, $output_path . "pdf_layers_default.png");
// Disable drawing of content that is not optional (i.e. is not part of any layer).
$ctx->SetNonOCDrawing(false);
// Now render each layer in the input document to a separate image.
$ocgs = $doc->GetOCGs();
// Get the array of all OCGs in the document.
if ($ocgs != null) {
$sz = $ocgs->Size();