jQuery - identifying specific form data when there multiple forms -

i have page multiple forms on each containing 1 submit button. when button pressed, need use data various hidden elements on form.

passing data via ajax working me using code this...

$("body").on("submit", "form", function (event) {           var pm = $(this).serialize();           event.preventdefault();           $.post(             'urota3.php?' + pm              ) ..... 

the data correct form passed urota3 , well.
but...
need use data in event function , i'm not sure how @ it. had tried adding data section this....

$("body").on("submit", "form", {   id: $('input:hidden[name=id]').val() }, function (event) {... 

but of course picks data first form on pade, not 1 button pressed.
how can reference piece of data correct form?
thanks
steve

$("body").on("submit", "form", function (event) {       var pm = $(this).serialize();       pm[id] = $(this).find('input:hidden[name='+id+']').val();       event.preventdefault();       $.post(         'urota3.php?' + pm          )