<?php
$str = '/dav/files/admin/%C3%BC%C3%B6%C3%A4%C3%B6%C3%A4%C3%BC%C3%B6%C3%A4%C3%BB%C5%B7%C3%AE';
$rawstr = rawurldecode($str);
var_dump(
mb_detect_encoding($rawstr, ['UTF-8', 'ISO-8859-1']),
mb_detect_encoding($rawstr, ['ISO-8859-1', 'UTF-8']),
mb_check_encoding($rawstr, 'ISO-8859-1'),
mb_check_encoding($rawstr, 'UTF-8'),
);
preferences:
27.08 ms | 407 KiB | 5 Q