Print url to default featured image

Question

I'm trying to setup a fallback image for featured image.

The main problem I have is miss of filter for get_the_post_thumbnail_url(). I'm using this function to echo thumb url in many-many templates, because it is easy customizable. So, this is not a solution to make an if-condition for each usage. And even to set default image for blank featured image, because it may be changed.

I see that I might apply filter to get_post_thumbnail_id(), but most likely I need an external URL to this fallback image, hardcoded in this theme. But, even if I can't apply external image, how can I make default image for get_the_post_thumbnail_url() function?

Answer 1

I would say you can't, not possible. There is no filter for get_the_post_thumbnail_url() or get_post_thumbnail_id().

However you could apply a filter to get_metadata() which get_post_thumbnail_id() uses, and return the id of another attachment that you want to use as the default thumbnail. But I don't recommend this it's a bit hacky.

I think you should refactor your code and just make a function to check if get_post_thumbnail_id returns anything.

Answer 2

Perhaps hook into save_post?

1. check that featured image is NOT set during save
2. then set default featured image post_meta _thumbnail_id

Reference:

• https://codex.wordpress.org/Plugin_API/Action_Reference/save_post

• https://core.trac.wordpress.org/browser/tags/4.8/src/wp-includes/post-thumbnail-template.php#L34 (@see get_post_thumbnail_id)