Codeigniter中的Ajax请求

I have been trying to create an ajax request in codeigniter. I've seen this question: Simple Ajax/Codeigniter request but I wasn't able to absorb that as there were the answers in which people were using PHP inside Javascript. I didn't know it was possible, however I gave that a try but it seems like the PHP wasn't being executed.

So here are my questions:

1. Is it really possible to use PHP inside Javascript, or am I mistaken?
2. What's the right way to perform an Ajax request in Codeigniter? What I've tried is the following:

var param = {name : event_name, date : event_date, time : event_time};

            $.ajax({
                // As seen from the question here at stackoverflow.
                url : "<?php echo base_url('event/new_event'); ?>",
                type : 'POST',
                data : param,
                beforeSend : function(){ },
                success : function(){
                    alert("Event created! Feel free to add as much details as you want.");
                    namebox.val("");
                    $("#new-event-modal").find(".close").trigger('click');
                    window.location.href = "<php echo base_url('user/dashboard'); ?>";
                },
                complete : function(){ },
                error : function(){ }
            });

I know the possibility that I could hardcode the URL in the request but that wouldn't be a good practice!!