Subtractive Logic in Template Animation

subtractive_logic.txt

<form>
    <dl class="error" id="whatevsError">
        <dt>You have to do something about this</dt>
        <dd>The reason we ask you do do this is so that we can laugh all the way to the bank</dd>
    </dl>
    <dl>
        <dt><label for="whatevs">Whatevs:</label</dt>
        <dd><input type="text" name="whatevs" id="whatevs" /></dd>
    </dl>
</form>

To render this using PHP you might do something this:

$dom = $this->loadDocument($my_template);

if(!checkFormError('whatevs'))
    $dom->getElementById('whatevsError')->parentNode->removeChild($dom->getElementById('whatevsError'));