When adding several numbers it appears that they should add to zero. Unfortunatly they dont. For example:

<?

// This is a very simple representation of the problem

$ary[] = 54493.08;
$ary[] = 18900.58;
$ary[] = 45819.39;
$ary[] = 22901.79;
$ary[] = 13342.42;
$ary[] = -127799;
$ary[] = 1755;
$ary[] = -29413.01;
$ary[] = -0.25;
$ary[] = 0;

while(list($key,$val) = each($ary)){
  $total = $val + $total;
  echo "Value: $val Total: $total<br>\n";
}


?>

The running total returns;
Value: 54493.08 Total: 54493.08
Value: 18900.58 Total: 73393.66
Value: 45819.39 Total: 119213.05
Value: 22901.79 Total: 142114.84
Value: 13342.42 Total: 155457.26
Value: -127799 Total: 27658.26
Value: 1755 Total: 29413.26
Value: -29413.01 Total: 0.25000000001091
Value: -0.25 Total: 1.0913936421275E-011
Value: 0 Total: 1.0913936421275E-011


So you can see that 29413.26 + -29413.01 doesnt equal 0.25 as it should.

mn