$(document).ready(function(){ 
	$('select[name=model_id]').change(function(){ 
		var model_id = $('select[name=model_id] option:selected').val();
		
		$.getJSON("/ajax/forms/car-request.php?model=" + model_id, function(data){
			$.each(data, function(i,item){
				$('select[name=class_' + i + '] option').remove();
				for(var ind = 0; ind < item.length; ind++) {
					$('select[name=class_' + i + ']').append('<option value="' + item[ind].name + '">' + item[ind].name + '</option>');
				}
    		});
		});
		
	});
});