Adding Titles and Captions to Relevanssi Index

add_filter('relevanssi_content_to_index', 'add_extra_content', 10, 2);
function add_extra_content($content, $post) {
  	$images = get_field_object('gallery', $post->ID);
  	if($images){
    	foreach( $images as $image ) {
	      	$content .= " " . $image['title'];
	      	$content .= " " . $image['caption'];
	    }
    	return $content;
	}
}