Weird Result from Decimal Calculation

[zelosnhp]

Found out that the result was different when I execute below simple calculation.

$total_percentage = 33.4 + 33.3 + 33.3;
if ($total_percentage < 100) {
echo "Total less than " . $total_percentage;
} else {
if ($total_percentage > 100) {
echo "Total more than " . $total_percentage;
} else {
echo "Total is " . $total_percentage;
}
}

The result is weird: Total less than 100

But if I simply change the sequence to:
$total_percentage = 33.3 + 33.3 + 33.4;
Or value of first 2 to:
$total_percentage = 33.5 + 33.2 + 33.3;

Then both result is correct as expected: Total is 100

And if want to remain the sequence and i add with number_format:
if (number_format($total_percentage, 1) < 100) {

The result is also correct: Total is 100

This happen to all version of PHP from 4.0.6 to 8.3.10 and only if the value is 33.4 + 33.3 + 33.3;

What could be the possibility cause of this?

[SakiTakamachi]

This is due to floating point inaccuracies.

Floating point numbers are imprecise, for example 0.1 + 0.2 does not equal 0.3.

So this is not a PHP issue, but a limitation of the float data type.

This is not a bug, but a feature of floating point numbers. If you want accurate calculations, we recommend using the BCMath extension.

[cmb69]

Oops, apparently my comment went into void.

All I have to add after @SakiTakamachi's comment: see https://floating-point-gui.de/ for details.