Description:
------------
This continues bug report 43572 at http://bugs.php.net/bug.php?id=43572&edit=2
which discussion is incomplete, yet has been prematurely closed.

> The value that you expect (0) is obtained using float precision.
> (In C) PHP uses double, and with this type fmod() returns 1.3.

So, to be concrete:
$a = 6.5;  print gettype($a);  // double
$b = 1.3;  print gettype($b);  // double
$c = $a / $b; print gettype($c);  // double

$d = 5.0;  print gettype ($d);  // double
print $c - $d;                  // 0
print (gettype($c - $d));       // double
print ($c===$d) ? "same" : "different";  // same

print gettype ($b - fmod($a, $b));  // double
print $b - fmod($a, $b);  // 2.22044604925E-16


In other words, PHP's own (double) math shows that 6.5 / 1.3 === 5.0
Regardless of the internal representation and precision of 6.5 and 1.3, division of the former ($a) by the latter ($b) results in a double value identical to 5.0.
fMod should return 0 in this situation.

Csaba Gabor from New York
PS.  I would prefer that these comments be moved to bug 43572 and that it be reopened until the discussion is completed, rather than having multiple threads.