flush_rewrite_rules() not working with update_option_{$option}

Question

Will someone please explain to me why flushing doesn't work in my case. I added a custom settings page with a default value, but it doesn't work when I hit save changes. I use the admin_init hook to register settings like this.

register_setting(
                'my_general', 
                'my_general_settings', 
                array(
                    'default'   => 'hello',
                ) 
            );

I added sections and fields, and those work. Now I am having a problem with this. If I update or save the settings, the update_option_my_general_settings doesn't work. It isn't flushing the rules. Here is the function code I used inside this hook.

if ( $old_value === 'hello' || $value === 'hello' ) {
                // Flush rules
                flush_rewrite_rules();
            }

Remember I am supplying these arguments to the function $old_value, $value, $option

The filter mod_rewrite_rules adds the data to .htaccess after I manually refresh the permalinks inside settings. But the flush_rewrite_rules() doesn't seem to be refreshing the permalinks automatically.

What I want is that when the user updates the settings, the flush_rewrite_rules should be populated.

I really appreciate any help you can provide.

Answer 1

Just stumbled on this very issue. It indeed seems as if flush_rewrite_rules(); doesn't work in some cases. Haven't found out why yet, but here is the solution that does work for me:

add_action( 'update_option_myOptionName', function($old_value, $value){
    if(some_checks){
        delete_option( 'rewrite_rules' );
    }
}, 10, 2);

This approach found on (https://developer.wordpress.org/reference/functions/flush_rewrite_rules/) inforces the deletion of the cached rewrite rules and wordpress regenerates them whenever appropriate.

Hope that helps.