title: Php QR code is not working for long length string
body: <p>I'm trying to convert my xml string to QR code.But it's showing nothing..It's working for minimal length string..Is there any way to do this?? here is my code</p>
  
  <pre><code>    &lt;?php
      ob_start();
      include ('../includes/phpqrcode/qrlib.php');
  
      QRcode::png('&lt;?xml version="1.0" encoding="UTF-8" ?&gt;
  &lt;vlsm&gt;
  &lt;facility&gt;&lt;facility_id&gt;020175&lt;/facility_id&gt;
  &lt;facility_name&gt;Freda Rebecca Mine Clinic&lt;/facility_name&gt;
  &lt;facility_state&gt;Mashonaland Central&lt;/facility_state&gt;
  &lt;facility_district&gt;Bindura&lt;/facility_district&gt;
  &lt;facility_hub_name&gt;&lt;/facility_hub_name&gt;
  &lt;facility_sample_id&gt;&lt;/facility_sample_id&gt;
  &lt;facility_request_clinician_name&gt;&lt;/facility_request_clinician_name&gt;
  &lt;facility_request_clinician_phone_number&gt;&lt;/facility_request_clinician_phone_number&gt;
  &lt;facility_support_partner&gt;&lt;/facility_support_partner&gt;
  &lt;facility_physician_name&gt;&lt;/facility_physician_name&gt;
  &lt;facility_date_test_ordered_by_physician&gt;0000-00-00&lt;/facility_date_test_ordered_by_physician&gt;
  &lt;facility_sample_collection_date&gt;2017-03-06 06:00:00&lt;/facility_sample_collection_date&gt;
  &lt;facility_sample_collected_by&gt;&lt;/facility_sample_collected_by&gt;
  &lt;facility_mobile_numbers&gt;&lt;/facility_mobile_numbers&gt;
  &lt;facility_emails&gt;&lt;/facility_emails&gt;
  &lt;facility_test_urgency&gt;&lt;/facility_test_urgency&gt;
  &lt;/facility&gt;&lt;/vlsm&gt;', "test.png", "L", 4, 4);
  </code></pre>