Change HTML GET attributes format

I have a trouble while transformation some web shop. I am going to change filters form, but unfortunatelly by now it is created with multiselect and result address looks like that

url.com/argument1=value1&argument1=value2&argument1=value3

I would like to change form construction into checkbox, but right now the address looks like url.com/argument1=value1,value2,value3

How can I change this to let checkbox work like multiselect and returns address like first one?