How to avoid this?

[tonibarcelona]

How about what you had before, but

  if( ereg("\?alpha_filter_id=[0-9]+$", $_SERVER['REQUEST_URI']) ) {
    header('HTTP/1.1 301 Moved Permanently');
    header('Location:http://www.mysite.com/shop/');
  } 

That will catch the filter if it is the only variable. I think that is a brutal hack, but it's up to you.

Personally I think that you are worrying about nothing, in time google will get a decent index of your site and those things will filter away.

Many thanks for your proposal. Maybe it´s abrutal hack, but by now is the only i have... At what fileis better inserting this? Filter.php? index.php?, or maybe to make a new php file and hooking it at auto-load?

I worry about this because i have 23 "main pages" indexed at google with an alpha filte id!!! Very bad for the serps... That thisn´t happen to any other zen cart user?

[banswidthjunkie]

Personally I wouldn't put it anywhere. But you could try putting it where you had the bit of code that caused your site to continually loop.

[tonibarcelona]

mmm. what effects do you think that may cause? Worth than to have more than 30 main pages (every day the number arise) indexed??

[banswidthjunkie]

Yeah, I really wouldn't worry about it. If you are searching for your URL then all sorts of odd stuff can get indexed. What you want to worry about is tuning your site so that you get ranked on specific search terms, not a few multiple pages.

[tonibarcelona]

Many thanks for your code.
Finally, i added a file (xxxredirect.php); calling it into index.php, and for now (maybe tomorrow i detect some contraindications), all seems to be ok.
I included at xxxredirect.phph a redirection from www.mysite.com/shop/index.php to www.mysite.com/shop/ too

Many thanx