Php calculate float

Question

I have a strange mathematical calculation here. Hope someone will explain.

$a = 1.85/100;
$b = 1.5/100;
$c = 1.1/100;
$d = 0.4/100;
$e = 0.4/100;
$f = 0.4/100;
$g = 0.4/100;

$h = $a + $b + $c + $d + $e + $f + $g;

echo $h*100 ."<br>";
$i = $h-$a;
$i = $i-$b;
$i = $i-$c;
$i = $i-$d;
$i = $i-$e;
$i = $i-$f;
$i = $i-$g;

echo $i;

The last value $ishould be 0, but it returns 6.93889390391E-18.

Answer 1

Any idea to correct my equation to show an end result of 0.00?

Yes, round($i, 2)

The “discrepancies” are usually so small that rounding to two decimal places almost always solves the problem.

Answer 2

You should read this article:

What Every Computer Scientist Should Know About Floating-Point Arithmetic

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Answer 3

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