Add Weight to Entries (posts) within a Specific Category (taxonomy term) in SearchWP

searchwp-customizations.php

<?php

// Add Weight to Entries (posts) within a Specific Category (taxonomy term) in SearchWP.
// @link https://searchwp.com/documentation/knowledge-base/add-weight-category-tag-term/
add_filter( 'searchwp\query\mods', function( $mods ) {
	global $wpdb;

	// Taxonomy bonus weight Mods.
	$bonuses = [ [
		'term_id' => 37,  // Term ID to receive extra weight.
		'weight'  => 100, // How much extra weight for this term.
	], [
		'term_id' => 82,  // Term ID to receive extra weight.
		'weight'  => 200, // How much extra weight for this term.
	] ];

	$term_mods = [];

	foreach ( $bonuses as $bonus ) {
		$mod = new \SearchWP\Mod();
		$index_alias = $mod->get_foreign_alias();
		$mod->relevance( "IF((
			SELECT {$wpdb->prefix}posts.ID
			FROM {$wpdb->prefix}posts
			LEFT JOIN {$wpdb->prefix}term_relationships ON (
				{$wpdb->prefix}posts.ID = {$wpdb->prefix}term_relationships.object_id
			)
			WHERE {$wpdb->prefix}posts.ID = {$index_alias}.id
				AND {$wpdb->prefix}term_relationships.term_taxonomy_id = {$bonus['term_id']}
			LIMIT 1
		) > 0, {$bonus['weight']}, 0)" );

		$term_mods[] = $mod;
	}

	$mods = array_merge( $mods, $term_mods );

	return $mods;
} );