Weird != behavior

Tracer

Prior to the If statement I:

 settype($total_collected, "float");
settype($total_due, "float");

I'm using the following if statement:

  if($total_collected != $total_due)

This works 98% of the time... But sometimes It fails? I can echo both vars to the screen as being equal to "38.14" and the If statement is still failing?

Any Ideas?

Roger_Ramjet

Basic behaviour of floating point numbres - they are only ever approximate.

from the manual
"So never trust floating number results to the last digit and never compare floating point numbers for equality."

NogDog

You could use [man]sprintf/man to compare them to a specified number of decimals:

$precision = 3;  // number of decimal places;
if(sprintf("%.{$precision}f", $total_collected) == sprintf("%.{$precisiof}f", $total_due)) {

Roger_Ramjet

Why not just use real numbers: integers or decimals, decimals in this case probably.

NogDog

PHP does not have a "decimal" type, just integers, floats, strings, booleans and arrays. Anything numeric value with a fractional (decimal) part will be a float. To avoid the precision errors of floats, you need to either round or truncate them (either to integers or strings), or use the BCMath arbitrary precision functions.

Tracer

But of course.. I knew that I couldn't compare floats... Duhhh...

But this should work... No?

$myInteger1=round(($myFloat1 * 10), 0);
$myInteger2=round(($myFloat2 * 10), 0);
if ($myInteger1 == $myInteger2)
{ Do Something Fun }

And it's cleaner than sprintf

NogDog

Actually, because round() returns a float, you might want to make absolutely, positively sure by casting its result to an integer:

$myInteger1=(int)round(($myFloat1 * 10), 0);
$myInteger2=(int)round(($myFloat2 * 10), 0);
if ($myInteger1 == $myInteger2)
{ Do Something Fun }

It's probably not necessary, but it won't hurt.