Additional content every x comments

Question

Do you have any idea of is it possible to add some content every let’s say 5 comments in WordPress? I could use “more fields” plugin but it would create content after each and every comment. Something like replies containing advertisements, which occurs every 5 forum replies in PhpBB but for WordPress.

e.g.

- comment 1  
- comment 2  
- ...  
- comment 5  
- MY CONTENT    
- comment 6  
- ... 
- comment 10  
- MY CONTENT
- comment 11

Answer 1

Here's one approach using the following custom input arguments:

wp_list_comments( [
    '_inject_period'  => 5,
    '_inject_content' => [ 'AAA', 'BBB', 'CCC' ],
] );

where we setup the inject period and define the content to inject.

This could be supported by the following demo plugin that extends the \Walker_Comment class and enhances the start_el() method:

<?php
/**
 * Plugin Name: Comment Content Injector
 * Plugin URI:  https://wordpress.stackexchange.com/a/251247/26350
 */

add_filter( 'wp_list_comments_args', function( $args )
{   
    // Period - Validation
    if( 
           ! isset( $args['_inject_period'] ) 
        || ! is_int( $args['_inject_period'] )   
        || 0 === $args['_inject_period']  
    )
        return $args;

    // Content - Validation
    if( 
           ! isset( $args['_inject_content'] ) 
        || ! is_array( $args['_inject_content'] ) 
    )
        return $args;

    // Custom Walker
    $args['walker'] = new class extends \Walker_Comment
    {
        public function start_el( &$output, $comment, $depth=0, $args=array(), $id=0 )
        {
            static $instance = 0;
            static $key      = 0;

            $tag = ( 'div' == $args['style'] ) ? 'div' : 'li'; // see Walker_Comment

            // Inject custom content periodically
            if( 
                0 == ++$instance % absint( $args['_inject_period'] ) 
                && isset( $args['_inject_content'][$key] ) 
            ) {
                $output .= sprintf( 
                   '<%s class="injected">%s</%s>', 
                   $tag, 
                   $args['_inject_content'][$key], 
                   $tag 
                );
                $key++;
            }

            // Parent method
            parent::start_el( $output, $comment, $depth, $args, $id );
        }
    };

    return $args;
} );

We might also want to adjust this to a given comment depth by checking the $depth variable. We could also inject it after the parent method but currently it's before.

Note that here we use an anonymous class. Here's more info on how to extend it without it.

Another approach would be to use the comments_array filter or if you use a custom callback, adjust it to your needs.

Hope you can adjust it further to your needs!