shopping cart, changing products per page

[viveleroi0]

I have a php shopping cart that dynamically creates prev/next buttons to display 10 products per page. How can I have a drop-down list on the page that when changed and click "submit" the user c an change the number of products displayed per page? Instead of ten the want only five.
Right now, my php script displays mysql results using
shop.php?offset=0&limit=10

But I want the drop down menu to have options 5,10,15 and 20, so that it will automatically reload the current page setting
shop.php?offset=0&limit=15
or another number. How can I do this without redirecting them to another page to process the form data?

[MrAlaska]

What exactly is it you are trying to avoid? You have to reload the page to change the display. You would send them back to the page they are at except with the display changed, and load the page dynamically based on the requested value.