MySQL UPDATE query problems - php

Question

I have a super easy question. I have a form that echoes out a mySQL record that the user can update. I make my changes, and it tells me that the update is successful, but when I look at the table, the changes do not go through. What is the problem here?
This is the first script.
<?php
require_once("models/config.php");
?>
<table border=1>
<tr>
<td align=center>Edit Form</td>
</tr>
<tr>
<td>
<table>
<?
$personid=$_SERVER['QUERY_STRING'];
$order = "SELECT * FROM persons where personid='$personid'";
$result = mysqli_query($mysqli,$order);
$row = mysqli_fetch_array($result);
?>
<form method="post" action="edit_data.php">
<input type="hidden" name="id" value="<? echo "$row[personid]"?>">
<tr>Person ID:<? echo "$row[personid]"?></tr>
<tr>
<td>First Name</td>
<td>
<input type="text" name="firstname"
size="20" value="<? echo "$row[firstname]"?>">
</td>
</tr>
<tr>
<td>Surname</td>
<td>
<input type="text" name="surname" size="40"
value="<? echo "$row[surname]"?>">
</td>
</tr>
<tr>
<td align="right">
<input type="submit"
name="submit value" value="Edit">
</td>
</tr>
</form>
</table>
</td>
</tr>
</table>
</body>
</html>
Which then goes through to this:
<?
require_once("models/config.php");
$personid = $_POST['personid'];
$firstname = mysqli_real_escape_string($mysqli, htmlspecialchars($_POST['firstname']));
$surname = mysqli_real_escape_string($mysqli, htmlspecialchars($_POST['surname']));
$order = "UPDATE persons SET firstname='$firstname', surname='$surname' WHERE personid='$personid'";
$result = mysqli_query($mysqli,$order);
if (!$result) {
echo "Error entering data! <BR>";
echo mysql_error();
} else {
echo "User updated to $firstname $surname <BR>";
}
?>
Is there something I am missing here?
Thanks in advance.

Answer 1

You are sending a hidden input named id and trying to use a $_POST['personid']
correct that
You may also pay attention to the comments you had (SQL Injection's one at least)

Answer 2

Your form sends the id in the field id, while you refer to it as personid.
The reason why this appears to be working, is that the update in itself is correct. $personid is treated as an empty string, so the update correctly updates all records that have an empty personid, which is no record at all.

Answer 3

OK, so here is a revised script with prepared statements. The script is working in the sense that updates are being made to the records. Two questions:
1) is this safe from My-SQL injections?
2) This is updating records successfully, but now it is echoing out "Error entering data!", how come?
<?
require_once("models/config.php");
$personid = $_POST['personid'];
$firstname = mysqli_real_escape_string($mysqli, htmlspecialchars($_POST['firstname']));
$surname = mysqli_real_escape_string($mysqli, htmlspecialchars($_POST['surname']));
$order = "UPDATE persons SET firstname=?, surname=? WHERE personid=?";
$stmt = mysqli_prepare($mysqli, $order);
mysqli_stmt_bind_param($stmt, "ssi", $_POST['firstname'], $_POST['surname'], $_POST['personid']);
mysqli_stmt_execute($stmt);
$result = mysqli_query($mysqli,$stmt);
if (!$result) {
echo "Error entering data! <BR>";
echo mysqli_error($mysqli);
} else {
echo "User updated to $firstname $surname <BR>";
}
?>
I'm sure the second question is a rather boneheaded one - do I just reverse the conditions?