PHP Simple Math Calculation

Question

can help me to see this calculation? It suppose echo "equal"... but it give me "not equal"

<?php
$tl_pax = 1;
$ct_pax = 2;
$at_pax = 2;

$a = 0.5;
$b = 0.2;
$c = 0.2;
$d = 0.2;
$e = 0.2;
$f = 0.2;
$g = 0.2;
$h = 0.9;

$sum = $a + $b + $c + $d + ($e * $tl_pax) + ($f * $ct_pax) + ($g * $at_pax) + $h;

$total = 3;

if($total == $sum){
    echo 'equal: ' . $sum . ' - ' . $total;
}
else{
    echo 'not equal: ' . $sum . ' - ' . $total;
}
?>

Answer 1

This is the usual case of the rounding error associated with binary floating point numbers. There are numbers that can't be represented exactly in binary, and thus the result will be of by some margin. To read up on it, the wikipedia article about floating point numbers is great.

The usual pattern found in this case is to pick a delta and compare against it:

 if(abs($total - $sum) < 0.01)
   echo "equal";

You'll have to pick your delta appropiately according to the usecase.

Answer 2

Check if they have difference less than 0.00001

if(abs($total - $sum) < 0.00001){

http://sandbox.phpcode.eu/g/56905/6

This article shows you why is this happening