It seems like an easy problem to solve, but It's not as easy as it seems. I have this string in PHP:

////%postname%/

This is a URL and I never want more than one slash in a row. I never want to remove the slashes completely.

This is how it should look like:

/%postname%/

Because the structure could look different I need a clever preg replace regexp, I think. It need to work with URLS like this:

////%postname%//mytest/test///testing

which should be converted to this:

/%postname%/mytest/test/testing