update and show comment without reloading the webpage - php

Question

i have the following jquery code, which is link to a html form which is link to a php script. the form should submit and the jquery code should update the comment and show the comment as if the page was referesh. but nothing happens when i hit submit i cant seem to see where or what i am doing wrong.
<script type="text/javascript">
$(function() {
//When submit button clicked
$('#submit').click(function(){
//Getting data from input fields
var sentby_val = $('#sent_by').val();
var message_val = $('#message').val();
$.post('comment.php', { username: sentby_val, message: message_val }, function(return_data){
//Response from script when comment inserted to database
alert(return_data);
//Clean fields
$('#sent_by').val('<?php print $_SESSION['email']?>');
$('#message').val('');
});
});
});
</script>
here is the html form
<form action='comment.php' method='post' style="width: 422px">
<input type='hidden' id="sent_by" name='sent_by' value="<?php print $_SESSION['email']?>"/>
<input type='hidden' id="hidden_id" name='hidden_id' value='<?php print $picid;?>'/>
<textarea name='message' id="message" value="make your comment" style="width: 450px; height: 70px">make your comment</textarea><br/>
<input type='submit' name='sub' value='comment' id="submit" style="border-style:none; float:right;" />
</form>
here is the comment.php // which shouldnt really be the problem
<?
$name = $_POST['sent_by'];
$picid= $_POST['hidden_id'];
$message = $_POST['message'];
$sub = $_POST['sub'];
if ($sub){if($name&&$message&&$picid)
{
$insert = mysql_query("INSERT INTO comment (name,message,picid) VALUES ('$name','$message','$picid')" );
}
else
{
echo "Please enter a comment";
}
header("location:../profile.php?pic=$id");
?>
please help what am i missing or not seeing

Answer 1

Try this:
<script type="text/javascript">
$(function() {
//When submit button clicked
$('#submit').click(function(){
//Getting data from input fields
var sentby_val = $('#sent_by').val();
var message_val = $('#message').val();
$.post('comment.php', { username: sentby_val, message: message_val }, function(return_data){
//Response from script when comment inserted to database
alert(return_data);
//Clean fields
$('#sent_by').val('<?php print $_SESSION['email']?>');
$('#message').val('');
});
// Overrides default click handler.
// Without this the form will be submitted
return false;
});
});
</script>