title: PHP float calculation error when subtracting
body: <p>I have a very strange issue. If I subtract 2 float vars where one is the result of a mathematical operation I get a wrong value.</p>
  
  <p>Example:</p>
  
  <pre><code>var_dump($remaining);
  var_dump($this-&gt;hours_sub['personal']);
  echo $remaining-$this-&gt;hours_sub['personal'];
  </code></pre>
  
  <p>This it the output:</p>
  
  <pre><code>float 5.4
  float 1.4
  5.3290705182008E-15
  </code></pre>
  
  <p><strong>5.4-1.4</strong> should be <strong>4</strong>
  If I add the two values the result is correct.</p>
  
  <p>Where is my mistake?
  It can not be a rounding issue.</p>