Functions for custom weighting in Search WP

searchwp-custom-weight.php

/*
 * SearchWP Filter - Join the postmeta table so we can grab the resource publication date to add weight to it later.
 */
function hnn_searchwp_query_main_join( $sql, $engine ) {
	global $wpdb;
	if (isset($_GET['test']) && $_GET['test'] == 'true') {
		$meta_key = 'publication_date';  // the meta_key you want to order by
		$sql = $sql . " LEFT JOIN {$wpdb->postmeta} ON {$wpdb->posts}.ID = {$wpdb->postmeta}.post_id AND {$wpdb->postmeta}.meta_key = '{$meta_key}'";
	}
	echo $sql . '<br/><br/>';
	return $sql;
}
add_filter( 'searchwp_query_main_join', __NAMESPACE__ . '\\hnn_searchwp_query_main_join', 10, 2 );
/**
 * SearchWP Filter - Add search weight to more recently published resources
 */
function hnn_searchwp_add_weight_to_newer_posts( $sql ) {
	global $wpdb;
	if (isset($_GET['test']) && $_GET['test'] == 'true') {
		$modifier = 25;
		$sql .= " + ( 100 * EXP( ( 1 - ABS( ( UNIX_TIMESTAMP( {$wpdb->prefix}postmeta.meta_value ) - UNIX_TIMESTAMP( NOW() ) ) / 86400 ) ) / 1 ) * {$modifier} )";
	}
	echo $sql . '<br/><br/>';
	return $sql;
}
add_filter( 'searchwp_weight_mods', __NAMESPACE__ . '\\hnn_searchwp_add_weight_to_newer_posts' );