title: PHP Warning: A non-numeric value encountered need fix
body: <p>I got this error when doing action to create order
  PHP Warning:  A non-numeric value encountered in /home/elazbagr/mysite/wp-content/plugins/custom-point/custom_point.php on line 257</p>
  <p>where line 257 is</p>
  <pre><code>            $diff = $duration - $stored_date;
  </code></pre>
  <p>and this lines up and down</p>
  <pre><code>            $duration = get_option(&quot;wc_settings_tab_period_of_changes&quot;,true);
              //$today_date = date(&quot;Y/m/d&quot;);
              $diff = $duration - $stored_date;
              //$diff = abs(round($diff / 86400));
              if($duration == 0) {
  </code></pre>
  <p>please help me to fix this
  regards</p>