Using WordPress ‘get_{$adjacent}_post_where’ PHP filter

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The get_{$adjacent}_post_where WordPress PHP filter is used to modify the WHERE clause in the SQL for an adjacent post query. The dynamic part of the hook name, $adjacent, refers to the type of adjacency, either ‘next’ or ‘previous’.

Possible hook names include:

  • get_next_post_where
  • get_previous_post_where

Usage

add_filter( 'get_next_post_where', 'your_custom_function', 10, 5 );

function your_custom_function( $where, $in_same_term, $excluded_terms, $taxonomy, $post ) {
  // Your custom code here
  return $where;
}

Parameters

  • $where (string): The WHERE clause in the SQL.
  • $in_same_term (bool): Whether the post should be in the same taxonomy term.
  • $excluded_terms (int[]|string): Array of excluded term IDs. Empty string if none were provided.
  • $taxonomy (string): Taxonomy used to identify the term when $in_same_term is true.
  • $post (WP_Post): WP_Post object.

More information

See WordPress Developer Resources: get_{$adjacent}_post_where

Examples

Exclude Posts with Certain Meta Key

add_filter( 'get_next_post_where', 'exclude_posts_with_meta_key', 10, 5 );
function exclude_posts_with_meta_key( $where, $in_same_term, $excluded_terms, $taxonomy, $post ) {
  global $wpdb;
  $where .= " AND $wpdb->posts.ID NOT IN ( SELECT post_id FROM $wpdb->postmeta WHERE meta_key = 'exclude_from_adjacent' )";
  return $where;
}

Show Posts from Same Category

add_filter( 'get_previous_post_where', 'same_category_previous_post', 10, 5 );
function same_category_previous_post( $where, $in_same_term, $excluded_terms, $taxonomy, $post ) {
  $where .= " AND post_type = 'post' AND post_status = 'publish'";
  return $where;
}

Exclude Posts with a Custom Post Type

add_filter( 'get_next_post_where', 'exclude_custom_post_type', 10, 5 );
function exclude_custom_post_type( $where, $in_same_term, $excluded_terms, $taxonomy, $post ) {
  $where .= " AND post_type != 'custom_post_type'";
  return $where;
}

Exclude Posts from Specific Categories

add_filter( 'get_previous_post_where', 'exclude_specific_categories', 10, 5 );
function exclude_specific_categories( $where, $in_same_term, $excluded_terms, $taxonomy, $post ) {
  $excluded_categories = array( 5, 12, 20 ); // Category IDs to exclude
  $where .= " AND term_taxonomy_id NOT IN (" . implode( ',', $excluded_categories ) . ")";
  return $where;
}

Show Posts with a Specific Post Status

add_filter( 'get_next_post_where', 'specific_post_status', 10, 5 );
function specific_post_status( $where, $in_same_term, $excluded_terms, $taxonomy, $post ) {
  $where .= " AND post_status = 'draft'";
  return $where;
}