How can I retain get_post_type() in between consecutive searches after a search returns no results?

Question

I've been trying to find an answer to this, but I haven't found anyone asking the same question.

I have multiple custom post types, with each having its own archive page and search form. As they all use searchform.php, within that I have added the below to make sure each search form only returns results for its respective post type:

<?php $post_type = get_post_type(); ?>
<input type="hidden" name="post_type" value="<?php echo $post_type ?>" />

This works fine on, for example an ebooks custom post type archive page, until I get a search that returns no results. With no results being on the page, get_post_type() returns nothing, and so the next search will return a blank post_type= query string. As a result, it uses the default 'post' post type and returns posts instead of ebooks. This in effect permanently changes the post type to 'post' until I get to another search that returns no results at which the above repeats.

Is there a simple way I can retain the post type between these searches so the post type doesn't change? I've seen lots of posts about how to filter search results for a custom post type, but no one seems to mention this issue.

Answer 1

You can use get_query_var() to access the post type that was used for the search, and then add that as a hidden field on the search page.

Untested:

printf( 
    '<input type="hidden" name="post_type" value="%s" />', 
    get_query_var( 'post_type', get_post_type() ) 
);