BP_Friends_Friendship::search_users( string $filter, int $user_id, int|null $limit = null, int|null $page = null )

	public static function search_users( $filter, $user_id, $limit = null, $page = null ) {
		global $wpdb;

		// Only search for matching strings at the beginning of the
		// name (@todo - figure out why this restriction).
		$search_terms_like = bp_esc_like( $filter ) . '%';

		$usermeta_table = $wpdb->base_prefix . 'usermeta';
		$users_table    = $wpdb->base_prefix . 'users';

		$pag_sql = '';
		if ( !empty( $limit ) && !empty( $page ) )
			$pag_sql = $wpdb->prepare( " LIMIT %d, %d", intval( ( $page - 1 ) * intval( $limit ) ), intval( $limit ) );

		$bp = buddypress();

		// Filter the user_ids based on the search criteria.
		if ( bp_is_active( 'xprofile' ) ) {
			$sql = $wpdb->prepare( "SELECT DISTINCT d.user_id as id FROM {$bp->profile->table_name_data} d, {$users_table} u WHERE d.user_id = u.id AND d.value LIKE %s ORDER BY d.value DESC {$pag_sql}", $search_terms_like );
		} else {
			$sql = $wpdb->prepare( "SELECT DISTINCT user_id as id FROM {$usermeta_table} WHERE meta_value LIKE %s ORDER BY d.value DESC {$pag_sql}", $search_terms_like );
		}

		$filtered_fids = $wpdb->get_col($sql);

		if ( empty( $filtered_fids ) )
			return false;

		return $filtered_fids;
	}