billynoah - 3 months ago 17

PHP Question

I simply want to know if $x is evenly divisible by $y. For example's sake assume:

`$x = 70;`

$y = .1;

First thing I tried is:

`$x % $y`

This seems to work when both numbers are integers but fails if they are not and if

`$y`

`fmod($x,$y)`

Which returns equally confusing results, "0.099999999999996".

php.net states

`fmod()`

Returns the floating point remainder of dividing the dividend (x) by the divisor (y)

Well according to my calculator

`70 / .1 = 700`

Answer

One solution would be doing a normal *division* and then comparing the value to the next integer. If the result is that integer or very near to that integer the result is evenly divisible:

```
$x = 70;
$y = .1;
$evenlyDivisable = abs(($x / $y) - round($x / $y, 0)) < 0.0001;
```

This subtracts both numbers and checks that the absolute difference is smaller than a certain rounding error. This is the usual way to compare floating point numbers, as depending on how you got a float the representation may vary:

```
php> 0.1 + 0.1 + 0.1 == 0.3
bool(false)
php> serialize(.3)
'd:0.29999999999999999;'
php> serialize(0.1 + 0.1 + 0.1)
'd:0.30000000000000004;'
```

See this demo:

```
php> $x = 10;
int(10)
php> $y = .1;
double(0.1)
php> abs(($x / $y) - round($x / $y, 0)) < 0.0001;
bool(true)
php> $y = .15;
double(0.15)
php> abs(($x / $y) - round($x / $y, 0)) < 0.0001;
bool(false)
```