Sort SearchWP results by multiple (3) numeric Custom Field post meta values

functions.php

<?php

add_filter( 'searchwp_query_main_join', function( $sql, $engine ) {
	global $wpdb;

	$priority_1_meta_key = 'featured_meta_key';
	$priority_2_meta_key = 'secondary_meta_key';
	$priority_3_meta_key = 'tertiary_meta_key';

	$sql = $sql . " LEFT JOIN {$wpdb->postmeta} swpprimary ON {$wpdb->posts}.ID = swpprimary.post_id AND swpprimary.meta_key = '{$priority_1_meta_key}'";
	$sql = $sql . " LEFT JOIN {$wpdb->postmeta} swpsecondary ON {$wpdb->posts}.ID = swpsecondary.post_id AND swpsecondary.meta_key = '{$priority_2_meta_key}'";
	$sql = $sql . " LEFT JOIN {$wpdb->postmeta} swptertiary ON {$wpdb->posts}.ID = swptertiary.post_id AND swptertiary.meta_key = '{$priority_3_meta_key}'";

	return $sql;
}, 10, 2 );

add_filter( 'searchwp_query_orderby', function( $orderby, $engine ) {
	$my_order = 'DESC'; // use 'DESC' or 'ASC'

	$original_orderby = str_replace( 'ORDER BY', '', $orderby );

	if ( 'DESC' === $my_order ) {
		// Sort in descending order
		$new_orderby = "ORDER BY swpprimary.meta_value+0 DESC, swpsecondary.meta_value+0 DESC, swptertiary.meta_value+0 DESC, " . $original_orderby;
	} else {
		// Sort in ascending order; place empties last
		// @link http://stackoverflow.com/questions/2051602/mysql-orderby-a-number-nulls-last#8174026
		$new_orderby = "ORDER BY -swpprimary.meta_value+0 DESC, -swpsecondary.meta_value+0 DESC, -swptertiary.meta_value+0 DESC, " . $original_orderby;
	}

	return $new_orderby;
}, 30, 2 );