WordPress: PostPost Plugin To Append Content After Every Post (Or Append By Category)

The PostPost Plugin provides a powerful way to append dynamic content, such as Calls-to-Action (CTAs), to your blog posts based on categories or universally across your site. This is particularly useful for marketers and content managers who want to:

Target specific categories with tailored CTAs.
Update content dynamically across the entire site with minimal effort.

Here’s how you can leverage the plugin:

Use Case 1: Append Dynamic CTAs by Category

Imagine you run a blog with categories such as Fitness, Technology, and Lifestyle. Each category can have its own CTA:

Subscribe to Fitness Tips for the Fitness category.
Download the Latest Tech Guide for the Technology category.
Explore Our Lifestyle Products for the Lifestyle category.

Using the PostPost Plugin:

Create a new postpost entry for each category.
Use the meta box to select the specific categories in which the CTA should appear.
Save and let the plugin dynamically append the CTA to relevant posts.

Use Case 2: Add and Update Content Universally Across All Posts

If you want to add disclaimers, announcements, or promotional content to all blog posts:

Create a single postpost entry.
Select the All Posts option in the meta box.
Save and watch the content get dynamically appended to every post on your site.

When the content needs updating, edit the postpost entry, and the changes will reflect across all posts instantly.

PostPost Plugin Code

Below is the full plugin code, which you can use to implement this functionality on your WordPress site:

<?php
/*
Plugin Name: PostPost
Description: Create reusable Gutenberg content blocks (PostPost) to append seamlessly to blog posts.
Version: 1.1
Author: Douglas Karr
Author URI: 
*/

if ( ! defined( 'ABSPATH' ) ) {
    exit; // Exit if accessed directly.
}

class PostPostPlugin {

    public function __construct() {
        add_action( 'init', [ $this, 'register_postpost_cpt' ] );
        add_action( 'add_meta_boxes', [ $this, 'register_meta_box' ] );
        add_action( 'save_post', [ $this, 'save_meta_box_data' ] );
        add_filter( 'the_content', [ $this, 'append_postpost_to_content' ] );
        add_filter( 'wp_robots', [ $this, 'exclude_postpost_from_indexing' ] );
        add_filter( 'wp_sitemaps_post_types', [ $this, 'exclude_from_sitemap' ] );
    }

    // Register custom post type
    public function register_postpost_cpt() {
        $args = [
            'label' => 'PostPost',
            'public' => false,
            'show_ui' => true,
            'show_in_menu' => true,
            'supports' => ['title', 'editor', 'revisions', 'custom-fields'],
            'show_in_rest' => true,
        ];
        register_post_type( 'postpost', $args );
    }

    // Exclude from sitemaps
    public function exclude_from_sitemap( $post_types ) {
        unset( $post_types['postpost'] );
        return $post_types;
    }

    // Exclude from search engine indexing
    public function exclude_postpost_from_indexing( $robots ) {
        if ( is_singular( 'postpost' ) ) {
            $robots['noindex'] = true;
        }
        return $robots;
    }

    // Register the meta box
    public function register_meta_box() {
        add_meta_box(
            'postpost_meta_box',
            'PostPost Settings',
            [ $this, 'render_meta_box' ],
            'postpost',
            'side'
        );
    }

    // Render the meta box
    public function render_meta_box( $post ) {
        $selected_option = get_post_meta( $post->ID, '_postpost_option', true );
        $selected_categories = get_post_meta( $post->ID, '_postpost_categories', true );

        $categories = get_categories();

        wp_nonce_field( 'postpost_meta_box', 'postpost_meta_box_nonce' );

        echo '<label><input type="radio" name="postpost_option" value="all" ' . checked( $selected_option, 'all', false ) . '> All Posts</label><br>';
        echo '<label><input type="radio" name="postpost_option" value="categories" ' . checked( $selected_option, 'categories', false ) . '> Specific Categories</label><br><br>';

        echo '<div id="postpost-categories" style="' . ( $selected_option === 'categories' ? '' : 'display:none;' ) . '">';
        foreach ( $categories as $category ) {
            echo '<label><input type="checkbox" name="postpost_categories[]" value="' . $category->term_id . '" ' . ( is_array( $selected_categories ) && in_array( $category->term_id, $selected_categories ) ? 'checked' : '' ) . '> ' . $category->name . '</label><br>';
        }
        echo '</div>';

        echo '<script>
            document.querySelectorAll(\'input[name="postpost_option"]\').forEach(radio => {
                radio.addEventListener("change", function() {
                    document.getElementById("postpost-categories").style.display = this.value === "categories" ? "" : "none";
                });
            });
        </script>';
    }

    // Save meta box data
    public function save_meta_box_data( $post_id ) {
        if ( ! isset( $_POST['postpost_meta_box_nonce'] ) || ! wp_verify_nonce( $_POST['postpost_meta_box_nonce'], 'postpost_meta_box' ) ) {
            return;
        }

        if ( defined( 'DOING_AUTOSAVE' ) && DOING_AUTOSAVE ) {
            return;
        }

        if ( isset( $_POST['postpost_option'] ) ) {
            update_post_meta( $post_id, '_postpost_option', sanitize_text_field( $_POST['postpost_option'] ) );
        }

        if ( isset( $_POST['postpost_categories'] ) && is_array( $_POST['postpost_categories'] ) ) {
            update_post_meta( $post_id, '_postpost_categories', array_map( 'sanitize_text_field', $_POST['postpost_categories'] ) );
        } else {
            delete_post_meta( $post_id, '_postpost_categories' );
        }
    }

    // Append PostPost content to the_content
    public function append_postpost_to_content( $content ) {
        if ( is_singular( 'post' ) ) {
            $post_id = get_the_ID();

            $query = new WP_Query( [
                'post_type' => 'postpost',
                'posts_per_page' => -1,
            ] );

            $postpost_content="";

            if ( $query->have_posts() ) {
                while ( $query->have_posts() ) {
                    $query->the_post();

                    $option = get_post_meta( get_the_ID(), '_postpost_option', true );
                    $categories = get_post_meta( get_the_ID(), '_postpost_categories', true );

                    if ( $option === 'all' ) {
                        $postpost_content .= apply_filters( 'the_content', get_the_content() );
                    } elseif ( $option === 'categories' && has_category( $categories, $post_id ) ) {
                        $postpost_content .= apply_filters( 'the_content', get_the_content() );
                    }
                }
            }

            wp_reset_postdata();

            return $content . $postpost_content;
        }

        return $content;
    }
}

new PostPostPlugin();

How to Use This Code:

Copy and paste this code into a file named postpost-plugin.php.
Place the file in the wp-content/plugins/postpost/ directory.
Activate the plugin from the WordPress admin panel.
Create postpost entries with your CTAs or content and configure the settings.

This plugin provides a versatile solution for managing dynamic CTAs or global content updates, enhancing your content strategy easily and efficiently.