title: Using multiple PregReplace filters on a Zend Form element
body: <p>I want to be able to add multiple PregReplace filters on a single Zend Form element. 
  I can add one PregReplace filter using the code below:</p>
  
  <pre><code>$word = new Zend_Form_Element_Text('word');
  $word-&gt;addFilter('PregReplace', array(
          'match' =&gt; '/bob/', 
          'replace' =&gt; 'john'
      ));
  $this-&gt;addElement($word);
  </code></pre>
  
  <p>I've tried</p>
  
  <pre><code>$word = new Zend_Form_Element_Text('word');
  $word-&gt;addFilter('PregReplace', array(
          'match' =&gt; '/bob/', 
          'replace' =&gt; 'john'
      ));
  $word-&gt;addFilter('PregReplace', array(
          'match' =&gt; '/sam/', 
          'replace' =&gt; 'dave'
      ));
  $this-&gt;addElement($word);    
  </code></pre>
  
  <p>but this just meant only the second filter worked.</p>
  
  <p>How do I add multiple PregReplace filters?</p>