title: PHPExcel won't recalculate
body: <p>In my excel file, I have <code>B1=IF(A1&gt;0,"Greater than Zero",IF(A1&lt;0,"Less than Zero","Equal Zero"))</code>.
  I tried to retrieve <code>B1</code> information via <code>getCalculatedValue</code> after changing the <code>A1</code> value.</p>
  
  <p>I did this multiple times, but both echos return "Less than Zero"
  I don't understand why the second echo doesn't return "Equal Zero?"</p>
  
  <pre><code>/** Change A1 Value **/
  $objPHPExcel-&gt;getActiveSheet()-&gt;setCellValue('A1','=-1');
  
  /** Calculate and State B1 Value **/
  echo $objPHPExcel-&gt;getActiveSheet()-&gt;getCell('B1')-&gt;getCalculatedValue();
  
  /** Change A1 Value AGAIN **/
  $objPHPExcel-&gt;getActiveSheet()-&gt;setCellValue('A1','=0');
  
  /** Calculate and State B1 Value **/
  echo $objPHPExcel-&gt;getActiveSheet()-&gt;getCell('B1')-&gt;getCalculatedValue();
  </code></pre>