urn:ogc:def:crs:EPSG:6.18:3:3857 is wrong and should be urn:ogc:def:crs:EPSG:6.18.3:3857

[ianturton]

This comes from a typo in the specification document (https://portal.ogc.org/files/?artifact_id=50398) and is causing problems for clients trying to consume your output.

[mprins]

I think its this line:

tileserver-php/tileserver.php

Line 915 in eb571b5

<ows:SupportedCRS>urn:ogc:def:crs:'.$srs[0].'::'.$srs[1].'</ows:SupportedCRS>';