How to use posts_join_request filter in WordPress

Working with WordPress hooks can sometimes feel like magic, right? Today, let’s dive into the posts_join_request filter. A handy tool for caching plugins, this hook can be registered using add_filter. You can place your code in the functions.php of your active theme or better yet, in a custom WordPress Plugin. This way, when you update your theme, nothing breaks. At WePlugins, we always prefer creating custom plugins for such purposes.

Below, I’ve shared a few live examples to help you get started with this hook.

Example 1: Basic Implementation

Here, we define a function modify_posts_join_request_defaults that takes two parameters. We then register it using add_filter. The parameters include the hook name posts_join_request, the function name modify_posts_join_request_defaults, the priority, and the number of arguments.

    function weplugins_modify_posts_join_request_defaults($join, $query) { 
        // Update the $join variable according to your website requirements and return this variable.
        return $join; 
    }
    // add the filter
    add_filter( "posts_join_request", "weplugins_modify_posts_join_request_defaults", 10, 2 );
    

Example 2: Removing a Hook Callback

Sometimes, you may need to remove a registered hook. Here’s how you can use remove_filter to remove the posts_join_request filter. Ensure you provide the same callback function name, priority, and number of arguments while removing the hook.

    remove_filter( "posts_join_request", "weplugins_modify_posts_join_request_defaults", 10, 2 );
    

Example 3: Advanced Customization

In some scenarios, you may want to modify the $join conditionally. Below is an example demonstrating how you can achieve that based on certain conditions.

    function weplugins_custom_posts_join_request($join, $query) {
        if ( $query->is_main_query() && $query->is_home() ) {
            // Modify $join for the main query on the homepage
        }
        return $join;
    }
    add_filter( "posts_join_request", "weplugins_custom_posts_join_request", 10, 2 );
    

Parameters

Below are the 2 parameters required to use this hook.

• $join : (string) The JOIN clause of the query.
• $query : (WP_Query) The WP_Query instance (passed by reference).