htmlpurifier/library/HTMLPurifier/ConfigSchema/schema/AutoFormat.RemoveEmpty.txt

AutoFormat.RemoveEmpty
TYPE: bool
VERSION: 3.1.2
DEFAULT: false
--DESCRIPTION--
<p>
  When enabled, HTML Purifier will attempt to remove empty elements that
  contribute no semantic information to the document. The following types
  of nodes will be removed:
</p>
<ul><li>
    Tags with no attributes and no content, and that are not empty
    elements (remove <code>&lt;a&gt;&lt;/a&gt;</code> but not
    <code>&lt;br /&gt;</code>), and
  </li>
  <li>
    Tags with no content, except for:<ul>
      <li>The <code>colgroup</code> element, or</li>
      <li>
        Elements with the <code>id</code> or <code>name</code> attribute,
        when those attributes are permitted on those elements.
      </li>
    </ul></li>
</ul>
<p>
  Please be very careful when using this functionality; while it may not
  seem that empty elements contain useful information, they can alter the
  layout of a document given appropriate styling. This directive is most
  useful when you are processing machine-generated HTML, please avoid using
  it on regular user HTML.
</p>
<p>
  Elements that contain only whitespace will be treated as empty. Non-breaking
  spaces, however, do not count as whitespace.
</p>
<p>
  This algorithm is not perfect; you may still notice some empty tags,
  particularly if a node had elements, but those elements were later removed
  because they were not permitted in that context, or tags that, after
  being auto-closed by another tag, where empty. This is for safety reasons
  to prevent clever code from breaking validation. The general rule of thumb:
  if a tag looked empty on the way end, it will get removed; if HTML Purifier
  made it empty, it will stay.
</p>