metal:fill-slotThis attribute can occur only inside metal:use-macro element.
This explicitly tells PHPTAL to replace a defined slot with the content provided inside the metal:fill-slot attribute.
<span tal:condition="logged" metal:fill-slot="news_place">
<h2>user menu</h2>
<ul>
<li><a href="/user/action/inbox">inbox</a></li>
<li><a href="/user/action/new">new mail</a></li>
<li><a href="/user/action/disconnect">disconnect</a></li>
</ul>
</span>
Slots give the opportunity to define really customizable and reusable page templates with a simple push technology.
Slots work like variables, not like callbacks. metal:fill-slot in tal:repeat will keep overwriting same slot over and over again.