How to identify if referrer is a 301 redirect

Question

I\'m implementing a slug system for my website at the moment. I plan to redirect invalid slugs to the correct on that is stored in the database. E.g.

Answer 1

Found a working solution:

• Start session.

• Check session, if $_SESSION['INVALID_SLUG'] exists display message then unset session

  else

• Retreive slug from database e.g. /11/right-slug

• Get current URI e.g. /11/wrong-slug

• Compare, if different set $_SESSION['INVALID_SLUG'] and redirect to correct page

Any feedback? I realise this will not detect a 301 redirect itself more detect a trigger assosiated with the redirect.

Thanks for all the help.