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)