trying to update

This program is to be used at the end of each month to begin
the month with fresh values. When executed there are no
errors, the message "Records have been updated" is displayed,
but no records are changed?

<?php
$stat = mysql_connect("localhost","root","");
$stat = mysql_select_db("prerentdb");
$query = "SELECT name FROM payments Where apt='$apt'";
$stat = @mysql_fetch_assoc(mysql_query($query));
echo $stat["name"];
$result= mysql_query("select * from payments");
while($row=mysql_fetch_array($result))
{
$id=$row['id'];
$paidsum=$row['paidsum'];
$rentdue=$row['rentdue'];
$prevbal=$row['prevbal'];
$latechg=$row['latechg'];
// if no payment or partial payment, add $10 to latechg field
// and amount not paid to prevbal field
if ($paidsum < $rentdue)
{
$latechg = $latechg + 10;
$owe = $rentdue - $paidsum;
$prevbal = $prevbal + $owe;
}
// if over-payment and late field not "L", subtract over-payment
// from prevbal field
if ($paidsum > $rentdue && $late |= 'L')
{
$sub = $paidsum - $rentdue;
$prevbal = $prevbal - $sub;
}
// refresh every record - give every record the below values
$amtpaid = 0;
$hudpay = 0;
$tentpay = 0;
$datepaid = ' ';
$late = ' ';
$paidsum = 0;
$comments = ' ';

$sql = "UPDATE payments SET
$amtpaid, $prevbal, $hudpay, $tentpay, $datepaid, $late, $comments, $paidsum";

mysql_query($sql) ;
}
echo "Records have been updated";
?>

PHP:

 

Try turning on error reporting and outputting the result of the query :

 

A hint: which fields are you trying to update ?

UPDATE payments SET field1=$value1, field2=$value2, ..

Code (markup):

Update your code and it will most likely finally go through.

 

thanks for the advice, it's now working except for one thing - is the below expression not valid?
if ($paidsum > $rentdue && $late != 'L')

&& $late != 'L' is being ignored

 

Looks ok to me. What are the values you are working with ?