title: PHP_XLSXWriter questions
body: <p>I am using <a href="https://github.com/mk-j/PHP_XLSXWriter" rel="nofollow noreferrer">PHP_XLSXWriter</a>. <br />
  I want to do the following expected output:<br /><br />
  <a href="https://i.stack.imgur.com/3yB6O.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/3yB6O.png" alt="enter image description here"></a></p>
  
  <p>Here is my code:</p>
  
  <pre><code>&lt;?php
  include_once('./PHP_XLSXWriter-master/xlsxwriter.class.php');
  
  $writer = new XLSXWriter();
  $sheet_name = 'Sheet1';
  
  $header = array("A", "B", "C");
  
  $writer-&gt;writeSheetRow($sheet_name, $header);
  
  $writer-&gt;markMergedCell($sheet_name, $start_row = ?, $start_col = ?, $end_row = ?, $end_col = ?);
  
  $writer-&gt;writeToFile('test.xlsx');
  ?&gt;
  </code></pre>
  
  <p>How should control ? in my code? </p>