[PHPTAL] trouble with ne and strings

[Walter Cruz]

Hi all. I want to display the dates of the news on the screen only if
the date changed. I have the following template:

<span tal:define="global lastdate string:walter" />

<span tal:omit-tag="" tal:repeat="noticia noticias/data">
<h2 tal:content="noticia/materia_publicacao" >text replaced by item</h2>
<h2 tal:content="lastdate" >text replaced by item</h2>
<p tal:condition="php: lastdate ne noticia.materia_publicacao">
aqui
  <span tal:define="global lastdate noticia/materia_publicacao" />
</p>



<!--  <p tal:replace="noticia/materia_hora" >text replaced by item</p>
  <a tal:attributes="href noticia/materia_id"
tal:content="noticia/materia_titulo"></a>-->
</span>

But the tal:condition always return true!

What I can't understand, is that the h2 tags in the loop displays the
same! (I have 2 articles on the same date)

<h2>2007-03-29</h2>
<h2>2007-03-29</h2>
<p>
aqui
  </p>

Can someone help me?

[]'s
- Walter