Adds all "visible" custom fields to the custom search excerpt for Relevanssi, code is based on the indexing code used in Relevanssi to add these fields to the index.

functions.php

// Relevanssi add content to custom excerpts.
add_filter('relevanssi_excerpt_content', 'custom_fields_to_excerpts', 10, 3);
function custom_fields_to_excerpts($content, $post, $query) {

		$custom_fields = get_post_custom_keys($post->ID);
		$remove_underscore_fields = true;

		if (is_array($custom_fields)) {
			$custom_fields = array_unique($custom_fields);	// no reason to index duplicates
			foreach ($custom_fields as $field) {
				if ($remove_underscore_fields) {
					if (substr($field, 0, 1) == '_') continue;
				}
				$values = get_post_meta($post->ID, $field, false);
				if ("" == $values) continue;
				foreach ($values as $value) {
					if ( !is_array ( $value ) ) {
						$content .= " " . $value;
					}
				}
			}
		}

    return $content;
}

Awesome piece of code!

Works perfect! Thank you for posting this

Thank you!