FressRSS/app/views/javascript/nbUnreadsPerFeed.phtml

<?php
declare(strict_types=1);
/** @var FreshRSS_ViewJavascript $this */

$result = [
	'feeds' => [],
	'tags' => [],
];
foreach ($this->categories as $cat) {
	foreach ($cat->feeds() as $feed) {
		$result['feeds'][$feed->id()] = $feed->nbNotRead();
	}
}
foreach ($this->tags as $tag) {
	$result['tags'][$tag->id()] = $tag->nbUnread();
}
echo json_encode($result);