Using WordPress ‘comment_feed_join’ PHP filter

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The comment_feed_join WordPress PHP filter allows you to modify the JOIN clause of the comments feed query before it’s executed.

Usage

add_filter('comment_feed_join', 'your_custom_function', 10, 2);

function your_custom_function($cjoin, $query) {
    // your custom code here
    return $cjoin;
}

Parameters

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

More information

See WordPress Developer Resources: comment_feed_join

Examples

Add a custom table to the JOIN clause

This example adds a custom table called wp_custom_table to the JOIN clause.

add_filter('comment_feed_join', 'add_custom_table_to_join', 10, 2);

function add_custom_table_to_join($cjoin, $query) {
    global $wpdb;
    $cjoin .= " LEFT JOIN {$wpdb->prefix}custom_table ON {$wpdb->prefix}custom_table.comment_ID = {$wpdb->prefix}comments.comment_ID";
    return $cjoin;
}

Join with postmeta table

This example joins the postmeta table to filter comments by a specific post meta key and value.

add_filter('comment_feed_join', 'join_with_postmeta_table', 10, 2);

function join_with_postmeta_table($cjoin, $query) {
    global $wpdb;
    $cjoin .= " INNER JOIN {$wpdb->prefix}postmeta ON {$wpdb->prefix}comments.comment_post_ID = {$wpdb->prefix}postmeta.post_id";
    return $cjoin;
}