title: HTMLPurifier still strips allowed attribute
body: <p>Using HTMLPurifier I tried to filter my user submission from an FCKEditor. My intention is only to allow some HTML tags such as p, img, a, etc with some their own attributes (such as align or style). But the result is HTMLPurifier still strips the attributes. </p>
  
  <p>Doctype: XHTML 1.0 Transitional
  Encoding: UTF-8</p>
  
  <p>Here's my config:</p>
  
  <pre><code>require PATH_SYSTEM . 'libs/htmlpurifier/HTMLPurifier.standalone.php';
  $config = HTMLPurifier_Config::createDefault();
  $config-&gt;set('HTML.Allowed', 'p[align|style],strong,a[href|title|mailto],em,table[class|width|cellpadding],td,tr,h3,h4,h5,hr,br,u,ul,ol,li,img[src|width|height|alt|class],span[class],strike,sup,sub');
  $purifier = new HTMLPurifier($config);
  </code></pre>
  
  <p>And here's my PHP code:</p>
  
  <pre><code>foreach ($_POST as $post=&gt;$value)
  {
     $_POST[$post] = $purifier-&gt;purify($value);
  }
  </code></pre>
  
  <p>I also tried HTML.AllowedElements and HTML.AllowedAttributes but still produce the same result as my config above.</p>
  
  <p>Thank you.</p>