PDF Thumbnail erstellen

$upload = wp_upload_bits($_FILES['wp_custom_attachment']['name'], null, file_get_contents($_FILES['wp_custom_attachment']['tmp_name']));
            //print_r($upload);
                    
                $newname = $upload['file'] . '.jpg';
            
                if (!file_exists($newname)) //falls datei noch nicht vorhanden umwandeln und in $folder speichern
                {
                    // lese das pdf (erste seite)
                    $thump = new imagick($upload['file'] . '[0]');
                    // in jpg umwandeln
                    $thump->setImageColorspace(255);
                    $thump->setCompression(Imagick::COMPRESSION_JPEG);
                    $thump->setCompressionQuality(60);
                    $thump->setImageFormat('jpeg');
                    // verkleinern
                    $thump->resizeImage(290, 375, imagick::FILTER_LANCZOS, 1);
                    // auf dem server speichern
                    $thump->writeImage($newname);
                    $thump->clear();
                    $thump->destroy();
                }
                else {
                    print 'konnte Thumb nicht erstellen!';
                }
            if(isset($upload['error']) && $upload['error'] != 0) {  
                wp_die('There was an error uploading your file. The error is: ' . $upload['error']);  
            } else {  
                $url = $upload['url'] . '.jpg';
                $tmp = download_url( $url );
                //print $url . ' - ';
                //print_r($tmp);
                   preg_match('/[^\?]+\.(jpg|JPG|jpe|JPE|jpeg|JPEG|gif|GIF|png|PNG)/', $file, $matches);
                $file_array['name'] = basename($matches[0]);
                $file_array['tmp_name'] = $tmp;
            
                // If error storing temporarily, unlink
                if ( is_wp_error( $tmp ) ) {
                    @unlink($file_array['tmp_name']);
                    $file_array['tmp_name'] = '';
                }
                $aid = media_handle_sideload( $file_array, $id, time().'-'.$_FILES['wp_custom_attachment']['name'] );
                update_post_meta( $id, '_thumbnail_id', $aid );
                add_post_meta($id, 'wp_custom_attachment', $upload);  
                update_post_meta($id, 'wp_custom_attachment', $upload);  
            }