title: Floating point subtraction issue in PHP
body: <p>This is a very simple issue to duplicate. I am doing a simple subtraction using floating point numbers.  As you can see from the code below and the corresponding output, the calculation is not correct. </p>
  
  <p>(php 5.6.6 on OSX El Capitan)</p>
  
  <pre><code>&lt;?php
  
      $bal = 20017.1;
      $amt = 20000;
      $newbal = $bal - $amt;
  
      print_r(compact('bal', 'amt', 'newbal'));
      echo "\n";
  </code></pre>
  
  <p>As you can see from this output, $newbal is not correct.</p>
  
  <pre><code>Array
  (
      [bal] =&gt; 20017.1
      [amt] =&gt; 20000
      [newbal] =&gt; 17.099999999999
  )
  </code></pre>