Horde_Mime_Part::getContentId PHP Method

    public function getContentId()
    {
        return ($hdr = $this->_headers['content-id']) ? trim($hdr->value, '<>') : null;
    }

 /**
  * Process a message again to add body and attachment data.
  *
  * @param \Horde_Imap_Client_Data_Fetch $messagedata The structure and part of the message body
  * @param \Horde_Mime_Part $partdata The part data
  * @param string $part The part ID.
  * @param string $filename The filename of the attachment
  * @return \stdClass
  * @throws \core\message\inbound\processing_failed_exception If the attachment can't be saved to disk.
  */
 private function process_message_part_attachment($messagedata, $partdata, $part, $filename)
 {
     global $CFG;
     // If a filename is present, assume that this part is an attachment.
     $attachment = new \stdClass();
     $attachment->filename = $filename;
     $attachment->type = $partdata->getType();
     $attachment->content = $partdata->getContents();
     $attachment->charset = $partdata->getCharset();
     $attachment->description = $partdata->getDescription();
     $attachment->contentid = $partdata->getContentId();
     $attachment->filesize = $messagedata->getBodyPartSize($part);
     if (!empty($CFG->antiviruses)) {
         mtrace("--> Attempting virus scan of '{$attachment->filename}'");
         // Store the file on disk - it will need to be virus scanned first.
         $itemid = rand(1, 999999999);
         $directory = make_temp_directory("/messageinbound/{$itemid}", false);
         $filepath = $directory . "/" . $attachment->filename;
         if (!($fp = fopen($filepath, "w"))) {
             // Unable to open the temporary file to write this to disk.
             mtrace("--> Unable to save the file to disk for virus scanning. Check file permissions.");
             throw new \core\message\inbound\processing_failed_exception('attachmentfilepermissionsfailed', 'tool_messageinbound');
         }
         fwrite($fp, $attachment->content);
         fclose($fp);
         // Perform a virus scan now.
         try {
             \core\antivirus\manager::scan_file($filepath, $attachment->filename, true);
         } catch (\core\antivirus\scanner_exception $e) {
             mtrace("--> A virus was found in the attachment '{$attachment->filename}'.");
             $this->inform_attachment_virus();
             return;
         }
     }
     return $attachment;
 }