title: Google cloud print. how to submit valid capabilities?
body: <p>When i sending a printer job without capabilities, it's work and print:</p>
  
  <pre><code>&lt;?php
  $url = "http://www.google.com/cloudprint/submit?printerid=" . $printer_id . &amp;output=json";
          $post = array(
              "printerid" =&gt; $printer_id,
              "capabilities" =&gt; '',
              "contentType" =&gt; "text/plain",
              "title" =&gt; $title,
              "content" =&gt; $docBytes
          );
          $post = http_build_query($post);
          $ret = $this-&gt;processRequest($url, $post, "");
  ?&gt;
  </code></pre>
  
  <p>But now i need to print information in A7 format letter. So i wrote this code with some capabilities:</p>
  
  <pre><code>&lt;?php
   $url = "http://www.google.com/cloudprint/submit?printerid=" . $printer_id . "&amp;output=json";
          $post = array(
              "printerid" =&gt; $printer_id,
              "capabilities" =&gt; array('psk:MediaSizeWidth' =&gt; '74000', 'psk:MediaSizeHeight' =&gt; '104700'), 
              "contentType" =&gt; "text/plain",
              "title" =&gt; $title,
              "content" =&gt; $docBytes
          );
  
          $post = http_build_query($post);
          $ret = $this-&gt;processRequest($url, $post, "");
  ?&gt;
  </code></pre>
  
  <p><strong>And it's don't want to print. Just Error. Maybe someone know how to right way to do this?</strong></p>