With the following code in functions.php – wp_get_attachment_metadata() returns false and or empty. Perhaps I am attempting to use wp_get_attachment_metadata() before it’s ready? As some tests have shown when manually add a previously added $attachement_ID I get the desired information..
function my_custom_attachment($attachment_ID) {
$meta = wp_get_attachment_metadata($attachment_id); // returns false
}
add_action('add_attachment', 'my_custom_attachment');
add_attachmentruns right after an attachment is added to the DB, but but before the metadata is generated. If you don’t need the value to be in the database yet, you can use thewp_generate_attachment_metadatafilter to hook in. However, if you need the data to be in the database already, you’ll have to useupdated_post_metaand check that themeta_keypassed in equals_wp_attachment_metadata.