- var_dump: documentation ( source)
- preg_replace: documentation ( source)
<?php
$path = '/www/nikita/tickets/web/img/news/29/29/promo_cover.jpg';
$matches = [];
var_dump([
'result' => preg_replace('/(.*)\/img\/news\/(\d+)\/(\d+)\/promo_cover\.jpg/', 'http://tickets.bp.ua', $path),
]);