How do I remove http, https and slash from user input in php

Question

Example user input

http://domain.com/
http://domain.com/topic/
http://domain.com/topic/cars/
http://www.domain.com/topic/questions/

I want

Answer 1

' . str_replace($removeprotocols,"",$url0);
echo '
' . str_replace($removeprotocols,"",$url1);
echo '
' . str_replace($removeprotocols,"",$url2);
echo '
' . str_replace($removeprotocols,"",$url3);

?>