Support for theming in PHP templates has been dropped.
True theming should support theme inheritance, e.g. mytheme <- table <- default.
Currently, the Templating component does not support such inheritance. As the
only purpose of the themes so far was to style field groups with tables or
divs, and because automatic rendering of field groups/forms through the render()
method is discouraged and only recommended for rapid prototyping, themes are
dropped for now.
Because that's just not possible (have a look at the unit tests to see all possibilities
-- as you will notice, there is no way we can determine the context and whether the
data are already escaped or not).
So, we always escape data, which means that sometimes, we will try to escape already
escaped data. This is not a problem for everything except strings. That's because
strings are not wrapped with an object like everything else (for performance reason).
This means that all escapers must be able to avoid double-escaping (that's the case
for the default escapers as both htmlspecialchars() and htmlentities() have a flag
that does just this).
Old notation: bundle:section:name.format:renderer (where both format and renderer are optional)
New notation: bundle:section:name.format.renderer (where only format is optional)
Valid new template names: Blog:Post:index.php, Blog:Post:index.xml.php
The new notation is more explicit and put all templating engines on the same level (there is no
more the concept of a "default" templating engine).
Even if the notation changed, the semantic has not. So, the logical template name for the above
examples is still 'index'. So, if you use a database loader for instance, the template
name is 'index' and everything else are options.
Upgrading current applications can be easily done by appending .php to each existing template
name reference (in both controllers and templates), and changing :twig to .twig for Twig templates
(for twig templates, you should also add .twig within templates themselves when referencing
another Twig templates).
