title: TCPDF adding digital signature to the created pdf
body: <p>I have kind of weird problem.<br> I'm struggling with a <code>pdf</code> digital signature problem since a while and it did't working as I expect. Actually it doesn't work at all. <br><br>I used exacly same code as is posted in the <code>Examples 52</code> page:</p>
  
  <pre><code>// set certificate file
  $certificate = 'file://var/www/app/tcpdf/config/cert/tcpdf.crt';
  
  // set additional information
  $info = array(
      'Name' =&gt; 'TCPDF',
      'Location' =&gt; 'Office',
      'Reason' =&gt; 'Testing TCPDF',
      'ContactInfo' =&gt; 'http://www.tcpdf.org',
      );
  
  // set document signature
  $pdf-&gt;setSignature($certificate, $certificate, 'tcpdfdemo', '', 2, $info);
  </code></pre>
  
  <p>First problem was about </p>
  
  <pre><code>Warning: openssl_pkcs7_sign() [function.openssl-pkcs7-sign]: error getting private key in /var/www/app/tcpdf/tcpdf.php on line 7566
  </code></pre>
  
  <p>It was caused because I did not set privileges to execute <code>cert</code> directory. But after I set <code>777</code> magic happen.<br> From now on I do not see what is the error, and I do not see the error track but:</p>
  
  <pre><code>HTTP ERROR 324 (net::ERR_EMPTY_RESPONSE)
  </code></pre>
  
  <p>anyone can suggest me something?</p>