title: php calculate float
body: <p>I have a weird math calculation here.  I hope someone will explain.</p>
  
  <pre><code>$a = 1.85/100;
  $b = 1.5/100;
  $c = 1.1/100;
  $d = 0.4/100;
  $e = 0.4/100;
  $f = 0.4/100;
  $g = 0.4/100;
  
  $h = $a + $b + $c + $d + $e + $f + $g;
  
  echo $h*100 ."&lt;br&gt;";
  $i = $h-$a;
  $i = $i-$b;
  $i = $i-$c;
  $i = $i-$d;
  $i = $i-$e;
  $i = $i-$f;
  $i = $i-$g;
  
  echo $i;
  </code></pre>
  
  <p>The last <code>$i</code> value should be 0 but it returns 6.93889390391E-18.</p>