Custom priority with the_content filter based on user input

Question

Currently, in my plugin Contextual Related Posts, I have an option to automatically add the related posts to the content using

add_filter('the_content,'ald_crp')

I know I can change the priority of the filter by adding a number greater than 10 (which is WordPress default).

add_filter('the_content,'ald_crp',20)

However, what I would like to do is let the user set the priority of the filter from within the options page which I can use and set the_content filter accordingly.

The plugin already has its own settings page.

My plugins doesn't use classes. It uses functions.

Any suggestions / code samples for this?

Answer 1

Save the priority in your options and pass that value to your add_filter:

add_action( 'template_redirect', 'wpse_81687_prepare_filter' );

function wpse_81687_prepare_filter()
{
    $my_options = get_option( 'my_options' );

    $priority = isset ( $my_options['content_filter_priority'] ) 
        ? $my_options['content_filter_priority'] 
        : 10;

    add_filter( 'the_content', 'ald_crp', $priority );
}

In my example I register the the_content filter during template_redirect because it is not needed earlier. You don’t need the filter in wp-admin or a login page.
You could even use the_post as hook instead of template_redirect. But then … another piece of code might call echo apply_filters('the_content', $some_text ); without calling setup_postdata() before.