<?php

for ( $i=0.01;$i<0.2;$i+=0.01) {
  echo (15+$i-15)."\n";
}
?>

i should have:
 0.01
 0.02
 0.03
 0.04
 0.05
....
 0.19

but i get :
0.00999999999998
0.02
0.0299999999999
0.0399999999999
0.0500000000001
0.06
0.07
0.08
0.09
...
0.19

A test on linux RedHat 6.2 and Windows 2000 SP3