In content-attachment.php I have:

/* preview for PDFs*/
if ('' === $ai) {
  wp_generate_attachment_metadata( $the_ID, wp_upload_dir() );
}

And it throws this error:

Fatal error: Call to undefined function wp_generate_attachment_metadata() in /home/content/xx/html/example/wp-content/themes/twentyseventeen-child/template-parts/post/content-attachment.php on line 110

Per another question here, I tried adding the following to the top of this file:

require_once( ABSPATH . 'wp-admin/includes/image.php' );

And that generates a slew of errors like this:

Warning: preg_match() expects parameter 2 to be string, array given in /home/content/55/8933555/html/seatacnoise/wp-includes/functions.php on line 2797

Now what?

In content-attachment.php I have:

/* preview for PDFs*/
if ('' === $ai) {
  wp_generate_attachment_metadata( $the_ID, wp_upload_dir() );
}

And it throws this error:

Fatal error: Call to undefined function wp_generate_attachment_metadata() in /home/content/xx/html/example/wp-content/themes/twentyseventeen-child/template-parts/post/content-attachment.php on line 110

Per another question here, I tried adding the following to the top of this file:

require_once( ABSPATH . 'wp-admin/includes/image.php' );

And that generates a slew of errors like this:

Warning: preg_match() expects parameter 2 to be string, array given in /home/content/55/8933555/html/seatacnoise/wp-includes/functions.php on line 2797

Now what?

• images
• attachments
• pdf

1 Answer 1

Despite you already solved it (the "undefined" issue), it should be noted that wp_generate_attachment_metadata() is defined in wp-admin/includes/image.php, so you need to manually load that file if you're using the function on the front-end, i.e. public side of the site or non admin/wp-admin pages (e.g. single attachment pages).

And in fact, the function reference says that:

If this function is undefined in the environment where it is to be used, such as within a Shortcode, use the include function:

if ( ! function_exists( 'wp_crop_image' ) ) {
  include( ABSPATH . 'wp-admin/includes/image.php' );
}

(You may use wp_generate_attachment_metadata instead of that wp_crop_image)

Secondly, you're not properly using the function:

wp_generate_attachment_metadata( $the_ID, wp_upload_dir() );

Because the second parameter for wp_generate_attachment_metadata() should be the attachment file path, and not an array (wp_upload_dir() returns an array) or anything else. So for example:

$file = '/full/path/to/the/attachment/file.pdf';
wp_generate_attachment_metadata( $the_ID, $file );

And make sure the file path is valid and that the $the_ID has the correct attachment post ID.