- implode: documentation ( source)
- explode: documentation ( source)
- parse_url: documentation ( source)
<?php
$url = "https://files.justimmo.at/public/pic/small/AYVHEJz-jk.jpg";
$parts = parse_url($url);
$path = explode('/',$parts['path']);
$path[1] = 'orig';
$parts['path'] = implode('/',$path);
echo http_build_url($parts);