Script:

<?
$a=10.87;
$b=10.31;

$c = $a + $b;

echo "a=$a<BR>";
echo "b=$b<BR>";
echo "c=$c<BR>";
?>

*************************
Result in PHP3:

a=10.87
b=10.31
c=21.18
*************************
Result in PHP4:

a=10
b=10
c=20
*************************

WWW server: Apache 1.3.12 Win32
PHP version: PHP 4.0.0 - Win32 Distribution