title: wkhtmltopdf Issue
body: <p>1) I uploaded"wkhtmltopdf-i386" to my server in a folder named "/pdf"</p>
  
  <p>2) I uploaded the php integration script, in the same folder, and named it "wkhtmltopdf.php" (http://code.google.com/p/wkhtmltopdf/wiki/IntegrationWithPhp)</p>
  
  <p>3) I uploaded a file that I named "usage.php", in the same folder, containing :</p>
  
  <pre><code>&lt;?php
  require_once('wkhtmltopdf.php');
  $pdf=new WKPDF();
  $pdf-&gt;set_html('Hello world!');
  $pdf-&gt;render();
  $pdf-&gt;output(WKPDF::$PDF_EMBEDDED,'sample.pdf');
  ?&gt;
  </code></pre>
  
  <p>4) I created a /tmp folder with 777 permissions (all).</p>
  
  <p>When I load usage.php, I get the following error:</p>
  
  <pre><code>"Fatal error: Uncaught exception 'Exception' with message 'WKPDF didn't return any data. &lt;pre&gt;&lt;/pre&gt;' in /home/***/public_html/dev/pdf/wkhtmltopdf.php:205 Stack trace: #0 /home/***/public_html/dev/pdf/usage2.php(5): WKPDF-&gt;render() #1 {main} thrown in /home/***/public_html/dev/pdf/wkhtmltopdf.php on line 205"
  </code></pre>
  
  <p>For your info, a html page is rendered in /tmp folder each time I load usage.php.</p>
  
  <p>Do you have any clue on how to solve my issue?</p>
  
  <p>Thanks</p>