Well, if you creat a session to identify which user it is, then make a UpdateUser.php or something. On that page, read their data in from the database and post it into a form like so:
<?
$UserName = username from the database
$Password = password from the database
$ICQ = icq # from the database
?>
<form action="SomePage.php" method="post">
Username: <?=$UserName?>
Password: <input type="password" name="Password" value="<?=$Password?>">
Verify Password: <input type="password" name="Password2" value="<?=$Password?>">
ICQ #: <input type="text" name="ICQ" value="<?=$ICQ?>">
<input type="submit" name="Submit" value="Update">
</form>
So, what that does it prints a form where the user can enter new data and update the account. It also populates the form with the users info from the database when s/he goes to the page. You have two password fields so that you can later make sure that the passwords match, to prevent users not being able to login due to type-o's. So, from there, you submit the form to a page that will update everything in the database.
<?
if ($_POST['Password'] != $_POST['Password2'])
{
echo "Your passwords do not match, please press the back button and try again.";
}
else
{
--open the database and update the users row
}
