title: mPDF temporary file is not writable using Yii
body: <p>I tried to print a certificate in PDF but when I push my code to staging, it said </p>
  
  <pre><code>Temporary files directory "/var/www/protected/vendor/mpdf/mpdf/src/Config/../../tmp" is not writable
  </code></pre>
  
  <p>I'm not sure how to change the permission and how to change the custom directory.</p>
  
  <p>Here's my code of a button to click to get the certificate:</p>
  
  <pre><code> &lt;a class="btn btn-sd btn-sd-ghost btn-sd-ghost-black margin-right-lg" href="&lt;?php echo $this-&gt;createUrl('//idea/frontend/pdf', array('id'=&gt;$model-&gt;id))?&gt;" target="_blank"&gt;Get Your Certificate&lt;i class="icon-right-small"&gt;&lt;/i&gt;&lt;/a&gt; 
              &lt;?php endif; ?&gt;
  </code></pre>
  
  <p>and this is the controller:</p>
  
  <pre><code>public function actionPdf($id){
          $model = HUB::getOrganization($id);
          $orgtitle = $model-&gt;title;
  
          $mpdf = new \Mpdf\Mpdf(['mode' =&gt; 'utf-8', 'format' =&gt; 'A4-L']);
          $mpdf-&gt;WriteHTML("&lt;html&gt;&lt;body style='background-image:url(\"/images/cert-idea.jpg\"); background-image-resize: 5; background-position: top center;'&gt;&lt;/body&gt;&lt;/html&gt;");
  
          $mpdf-&gt;WriteHTML("&lt;div style='text-align:center; display:table; height:100%; width:100%; padding-top:28%;'&gt;&lt;h1 style='display:table-cell; vertical-align:middle; font-size:40px;'&gt;".$orgtitle."&lt;/h1&gt;&lt;/div&gt;");
  
  
          $mpdf-&gt;Output('IDEA-CERT-'.$orgtitle.'.pdf', 'I');
      }
  </code></pre>
  
  <p>Hope someone can help on my issue. Thank you!</p>