problem with multipart/form-data

problem with multipart/form-data

I'm trying to send a form via jquery/ajax into a php file, where i could export each data separably.
My js code: 
  2. $.ajax({
  3.   type: "POST",
  4.   url: "upload/uploadimage",
  5.   data: $("#uploadform").serialize(),

  7. success: function(data){
  8.    $('#uploadStatus'+position).hide();
  9. $('#uploadStatus'+position).html(data).fadeIn(1500, function(){
  10. $('#uploadStatus'+position).append("");
  11. });
  12.   }
  13.   });
and this is my form
  1. <form action="" method="post" enctype="multipart/form-data" name="uploadform" id="uploadform">
  2.  <p><input type="FILE" id="userfile" name="userfile" /></p>  
  3.  <p><input type="BUTTON" value="Upload Selected File" id="submit" name="submit" /></p>
  4.  </form> 

The problem is - it does not work as i imagined it. My question is - how to send multipart/form-data in a pattern of: form -> ajax -> php.