Description:
------------
When adding a float value to a variable (starting with a negative value) in a loop the result that should be zero (0) is nearly zero, but not exact zero.

Reproduce code:
---------------
<?php

for ($i = -1.0; $i <= 1.0; $i += 0.1) {
  echo $i . "\n";
}

?>

Expected result:
----------------
-1
-0.9
-0.8
-0.7
-0.6
-0.5
-0.4
-0.3
-0.2
-0.1
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1

Actual result:
--------------
-1
-0.9
-0.8
-0.7
-0.6
-0.5
-0.4
-0.3
-0.2
-0.1
-1.38777878078E-16
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1