function addToCart(id) {
   $('#buy_config_block_'+id).hide();
   $('#remove_cart_block_'+id).show();
   // ajax
   $.get('/transactions/addToCart',
	 {id:id,
	  start_date:$('#start_date_'+id).val(),
	  end_date:$('#end_date_'+id).val()},
	  function(data) {
	  });
	     
   // update count
   shopping_cart_size=parseInt($('#shopping_cart_count').html());
   shopping_cart_size+=1;
   $('.shopping_cart_span').each(function(index) {
      $(this).html(shopping_cart_size+"");
     });
}

function removeFromCart(id) {
   $('#buy_config_block_'+id).show();
   $('#remove_cart_block_'+id).hide();
   // ajax
   $.get('/transactions/removeFromCart',
	 {id:id},
	 function(data) {
	 });

   // update count
   shopping_cart_size=parseInt($('#shopping_cart_count').html());
   shopping_cart_size-=1;
   if (shopping_cart_size<0) {
     shopping_cart_size=0;
   }
   $('.shopping_cart_span').each(function(index) {
       $(this).html(shopping_cart_size+"");
     });
}