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/**
 * ADDS FUNCTIONALITY TO SEARCH WITHIN ACF FIELDS
 * @link https://adambalee.com/search-wordpress-by-custom-fields-without-a-plugin/
 */

// Make the search to index custom
/**
 * Extend WordPress search to include custom fields
 * http://adambalee.com
 *
 * Join posts and postmeta tables
 * http://codex.wordpress.org/Plugin_API/Filter_Reference/posts_join
 */
function cf_search_join( $join ) {
  global $wpdb;
  if ( is_search() ) {
      $join .=' LEFT JOIN '.$wpdb->postmeta. ' ON '. $wpdb->posts . '.ID = ' . $wpdb->postmeta . '.post_id ';
  }
  return $join;
}
add_filter('posts_join', 'cf_search_join' );

/**
* Modify the search query with posts_where
* http://codex.wordpress.org/Plugin_API/Filter_Reference/posts_where
*/
function cf_search_where( $where ) {
  global $pagenow, $wpdb;
  if ( is_search() ) {
      $where = preg_replace(
          "/\(\s*".$wpdb->posts.".post_title\s+LIKE\s*(\'[^\']+\')\s*\)/",
          "(".$wpdb->posts.".post_title LIKE $1) OR (".$wpdb->postmeta.".meta_value LIKE $1)", $where );
  }
  return $where;
}
add_filter( 'posts_where', 'cf_search_where' );

/**
* Prevent duplicates
* http://codex.wordpress.org/Plugin_API/Filter_Reference/posts_distinct
*/
function cf_search_distinct( $where ) {
  global $wpdb;
  if ( is_search() ) {
      return "DISTINCT";
  }
  return $where;
}
add_filter( 'posts_distinct', 'cf_search_distinct' );