用ajax成功

var url = '<?php echo base_url(); ?>index.php/home_event/view_cal';
 $.ajax({
        type: "POST",
        url: url,
        secureuri      :false,
        dataType: "json",
        data: postData,
           success: function (data,event_name,event_description,start_date,location)    
           {

            $('.heading_bg').html(event_name);
            $('.location_details').html(location);
            $('.date_details').html(start_date);
            $('.event_content').html(event_description);
        }
    });
});  return false;
             });

in this code ,the success part doesnot replace my values in the form.i.e my event_name is not shown in heading_bg div.pleas help.

The first argument of the success function is going to contain all of your data. Try something like:

success: function(data) {
    $('.heading_bg').html(data.event_name);
    /* ... */
}

Or you can inspect data:

success: function(data) {
    console.dir(data);
}

Check the success argument here http://api.jquery.com/jQuery.ajax/