Can not get proper result for type casting in PHP

Question

I have a Float variable

$float = 37.80

Then I multiply the float by 100:

$mul = $float *100

Now I have 3780.

$typecasting = (int) $mul;

Now when I print $typecasting, it shows 3779

For example:

$float = 37.80;
$mul = $float*100;
echo $mul;
echo '<br>';
//$mul = 3780
$typecasting = (int) $mul;
echo $typecasting;
// $typecasting shows 3779

I can't understand, how it works. This problem occurs only for 32.80, 33.80, ...4.80. and also for multiples of 2, i.e. 65.60.

Floating points aren't perfect in any programming language. You found an example that shows this. https://stackoverflow.com/questions/2100490/floating-point-inaccuracy-examples . This happens because binary isn't perfect for storing halves, eights, sixteenths, etc. Just as you can't write 1/3 in the decimal system properly, you can't store `37.80` in binary properly. — Loek, Dec 21 '18 at 13:13

score 1 · Answer 1 · answered Dec 21 '18 at 13:14

1

$float = 37.80;
$mul = $float*100;
echo $mul;
echo '<br>';
//$mul = 3780
$typecasting = floatval($mul);
echo $typecasting;
// $typecasting shows 3779

answered Dec 21 '18 at 13:14

Ingus

1 Answers1