ignore URI fragment when dereferencing

[Tobion]

The URI fragment should be ignored when dereferencing a URI and is not meant to be sent.

Fragment identifiers have a special role in information retrieval
systems as the primary form of client-side indirect referencing,
allowing an author to specifically identify aspects of an existing
resource that are only indirectly provided by the resource owner. As
such, the fragment identifier is not used in the scheme-specific
processing of a URI; instead, the fragment identifier is separated
from the rest of the URI prior to a dereference, and thus the
identifying information within the fragment itself is dereferenced
solely by the user agent, regardless of the URI scheme.

https://tools.ietf.org/html/rfc3986#section-3.5

[Tobion]

This was only rewritten so phpstorm understands that $onHeaders can be a callable or null and does not mark this with an error.