How do I create a variable that I can use in both PHP and SS templates?

For example:

In my Page.php I can write a simple function:
   public function LatestNewsID() {
      return 150;
   }

This allows me to use that var in a SS template something like this:
<% if LatestNewsID = 150 %>
   Do something with $LatestNewsID
<% else %>
   Do something else
<% end_if %>

However, how do I reference the same variable in a PHP template?

jf/

Thanks for the help. But I have some odd behaviour going on on the SS template.

As before, I have this in Page.php:
public function LatestNewsID() {
return 150;
}

And in one of my include templates, SideBar.ss, I have a looping control element, a bit like this:

($LatestNewsID)
<% control Menu(1) %>
   [$ID] ** [$LatestNewsID]
   <% if Children %>
      <% control Children %>
         <li class="$LinkingMode"><a href="$Link" title="Go to the $Title.XML page" >$MenuTitle.XML</a></li>
      <% end_control %>
   <% end_if %>
<% end_control %>
($LatestNewsID)

Where it says $LatestNewsID in parenthesis, both before and after the control element, the value 150 prints to the page.
However, inside the control element, where $LatestNewsID is written in square brackets, the value is null.

Can I not call the function inside a control element?

jf/

Thanks Luke. Still got a problem though...

This prints to the page fine:
$ID ** $Top.LatestNewsID

However, on the next line, if I try to test against the function:
<% if ID != Top.LatestNewsID %>

I get this error:
Parse error: parse error in C:\WINDOWS\Temp\silverstripe-cacheC--wamp-www-OlafIntranet-SilverStripe
\.cacheC..wamp.www.OlafIntranet.SilverStripe.themes.olafIntranet03.templates.Page.ss on line 324

I tried deleting the cache file but it just recreated itself on the next page request.

Is there a different way of referring to a function or variable that is in the "Top" scope whilst inside a control loop?

jf/

^^ bump ^^