Generate all old PDF preview images with WordPress 4.7

WordPress 4.7 generates thumbnails for PDF files while uploading them in the media library, this is a really good thing…

December 13, 2016

WordPress 4.7 generates thumbnails for PDF files while uploading them in the media library, this is a really good thing especially if you have a site that uses PDF to publish some kind of contents (books, or lessons, documents or anything else) this can be really useful.

Even if, probably, you’ve already used┬áthe featured image to upload the first page of the PDF or a cover file.

To automatically create the images of all the PDF in your library, you have to trigger the file generation functions for all the file that you already have in your media library.

Here is a small script to process all your PDF files to generate thumbnails, there are two methods to call for each image:

1) wp_generate_attachment_metadata to generate the thumbnails
2) wp_update_attachment_metadata to store the new metadata generated in the database.

After running this script you will see the images in the media library an you can use the WordPress functions to show the attachments in your theme or plugin.

Place this file in the root. Run once and then remove it.

include 'wp-load.php';
include 'wp-admin/includes/image.php';
if ( !current_user_can( 'edit_others_pages' )) die("Not authorized.");
$attachments = $wpdb->get_results("select * from wp_posts where post_mime_type='application/pdf'");
if ($attachments) {
	foreach ($attachments as $attachment) {
		$filename = str_replace("http://".$_SERVER['HTTP_HOST'], $_SERVER['DOCUMENT_ROOT'], $attachment->guid);
		echo $filename."<br/>\n";
		$metadata = wp_generate_attachment_metadata($attachment->ID, $filename);
		wp_update_attachment_metadata($attachment->ID, $metadata);


I'm a software engineer, an everyday web developer and a maker. I usually build sites with PHP, within or without WordPress. I build Internet of Things with Arduino and ESP8266. I'm the founder of and and I'm actually the Chief Technical Officer of Better Days web agency.


Stop sending email to new user in WordPress admin registration

Prevent WordPress to send notification emails when you manually create new users

March 9, 2017

Add filter on wp_title not working with Yoast SEO plugin

For SEO purposes, in a specific template that has a list of items with pagination, I need to have different…

February 22, 2017

Clean up and optimize WordPress head tag

If you need to know how to remove RSS Feed URL’s from page head or how to remove post relational…

December 11, 2015

A new avatar generator for WordPress with get_avatar and Flathash

Brand new avatars for WordPress Gravatar service

April 7, 2017

3 ways to add author’s image in WordPress

Add author's image in WordPress without a plugin

April 5, 2017

Add Internet Explorer class to body to detect old browser

When you have clients that still uses an old browser, you need to handle it. This javascript function detects the…

February 27, 2017