Ajax form perfect until inside another page - ajax

Question

I have a page which uses ajax to submit a comment form, add it to a db, then redisplay the page, hopefully without reloading the page its on.
If I access the script on it's own it works great, yet when I load it into another page it doesn't add the data and also refreshes the page on submit, which I want to avoid, which is the whole point of doing things this way.
Anyway, here's how I load the page:
<div id="wall_comments" class="msgs_holder"></div>
<script type="text/javascript">
$('#wall_comments').load('/pages/comment.php', { wl_id:"<?=$wl_id?>" });
</script>
and then the page itself with jquery code:
<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.8.0/jquery.min.js" type="text/javascript"></script>
<div style="width:100%; overflow:auto;">
<form method=post>
<input type="text" class="inp" name="comment" id="comment">
<input type=submit value="do it" name="action" onclick="update()">
<input type=hidden name="wl_id" value="<?=$_REQUEST[wl_id]?>" id="wl_id">
<input type=hidden name="user_id" value="<?=$userfromcookie?>" id="user_id">
</form>
</div>
<script type="text/javascript">
function update(){
var wl_idVal = $("#wl_id").val();
var commentVal = $("#comment").val();
var user_idVal = $("#user_id").val();
$.ajax({
type: "POST",
url: "/pages/comment.php",
cache: false,
data: { submit: "", wl_id: wi_idVal, comment: commentVal, user_id: user_idVal }
});
}
</script>
And finally enter info into db (I know this should be mysqli and it will be)
if(isset($_POST['action'])){
$wl_id = mysql_real_escape_string($_POST['wl_id']);
$comment = mysql_real_escape_string($_POST['comment']);
$user_id = mysql_real_escape_string($_POST['user_id']);
$addcomment = mysql_query("insert into list_wall (
event_id,
user_id,
comment
) VALUES (
'$wl_id',
'$user_id',
'$comment'
) ",$db);
if(!$addcomment) { echo 'result error add comment'; echo mysql_error(); exit; } // debug
}

Answer 1

The problem is when you click the submit button, the page is submitted and the function update couldn't work. You have to cancel the default submit mechanism by using return false;
<input type=submit value="do it" name="action" onclick="update() return false;">

Answer 2

Another thing.
The onclick on the submitbutton will not work as excpected if the submit is caused without clicking the button.
For example mobile safari on iPhone can submit forms directly without triggering the button.
If you add UmairP's version of the onclick to the form element as an onsubmit method you should get the same result on every platform as far as I know.
You can see more details on iPhone forms in my own question on another issue.
How can I prevent the Go button on iPad/iPhone from posting the form