title: php code not executing inside do while() loop in php 5.5 wordpress 4.8
body: <p>This is the function related to DB Upgrade of wordpress plugin.<br>
  Code inside 'do' is not getting executed.
  This file is used to make alterations in plugin tables.
  Can someone help me with the issue ? </p>
  
  <p>php version is - 5.5 , wordpress - 4.8</p>
  
  <pre><code> public function upgrade($version)
   {
      @set_time_limit(300);
  
      if ($version === false || ((int)$version) &gt; WpProQuiz_Helper_DbUpgrade::WPPROQUIZ_DB_VERSION) {
          $this-&gt;install();
  
          return WpProQuiz_Helper_DbUpgrade::WPPROQUIZ_DB_VERSION;
      }
  
      $version = (int)$version;
  
      if ($version === WpProQuiz_Helper_DbUpgrade::WPPROQUIZ_DB_VERSION) {
          return WpProQuiz_Helper_DbUpgrade::WPPROQUIZ_DB_VERSION;
      }
  
      do {
          $f = 'upgradeDbV' . $version;
  
          if (method_exists($this, $f)) {
              $version = $this-&gt;$f();
          } else {
              die("WpProQuiz upgrade error");
          }
      } while ($version &lt; WpProQuiz_Helper_DbUpgrade::WPPROQUIZ_DB_VERSION);
  
      return WpProQuiz_Helper_DbUpgrade::WPPROQUIZ_DB_VERSION;
  }
  </code></pre>