PHP, TCPDF : Add timestamp to PDF signature

We generate a PDF and sign it (using the TCPDF library in PHP). We would like to add a timestamp to it (using the [login to view URL] service for example : [login to view URL]) 1/ Use the TCPDF example : [login to view URL] 2/ Remove everything we don't need... to basically keep a very simple text 3/ Re-write the protected function applyTSA($signature) from the TCPDF library so it adds timestamp from [login to view URL] You will basically have to send a application/timestamp-query query using CURL to the freetsa service and get back the result to use it to complete the signature. As a proof it's working fine, we simply expect to have a PDF file with the timestamp added to the signature. If you check the signature within a PDF reader, you should see the signature is valid (if you trust the origin) and the timestamp is not coming from the computer but from a valid source. We expect a clean code, no additional library, just TCPDF. Simply extend TCPDF (TCPDF2 extends TCPDF...) and override the applyTSA protected function... that should be enough!