I know it's an old thread, but still you find it among top 3 on Google, so here's a little update to it.
You can take different aproaches on creating a navigation with a "highlighting class" with Symfony.
1. Check route
As @Sebastian J suggested, you can check with an if else for the route.
<li{% if app.request.get('_route') == 'foo_products_overview' %} class="active"{% endif %}>
Problem: It's not officially supported, as @netmikey pointed out: How to get current route in Symfony 2?
1.1. Check route array
I actually use this on my projects, with one adjustment. I use an in array function, to be able to give more than one route.
<li{% if app.request.attributes.get('_route') in [
'foo_products_overview',
'foo_products_detail',
'foo_products_bar'
] %} class="active"{% endif %}>
1.2. Check route start with ...
A third approach would be what @bernland has suggested. Let's asume we want to match all routes starting with foo_products
and we'd like to apply this by magic.
<li{% if app.request.attributes.get( '_route' ) starts with 'foo_products' %} class="active"{% endif %}>
As I said, I use this and haven't had an issue, yet.
2. Use a Bundle/function
I'm sure there are other Bundles out there, but I'd recomend you this to create your navigation: https://github.com/KnpLabs/KnpMenuBundle
3. Use a macro
edit July 2015
My new favorite is to use a macro like
{% macro menuItem(name, url, subitems) %}
{% spaceless %}
{% set subitems = subitems|default({}) %}
{% set currentUrl = path(app.request.attributes.get('_route'), app.request.attributes.get('_route_params')) %}
{% set isActive = currentUrl == url %}
{% for name, suburl in subitems %}
{% set isActive = not isActive and currentUrl == suburl %}
{% endfor %}
<li{% if isActive %} class="is-active"{% endif %}>
<a href="{{ url }}"{% if subitems|length > 0 %} class="has-sub-menu"{% endif %}>{{ name|trans() }}</a>
{% if subitems|length > 0 %}
<ul class="main-sub-menu">
{% for name, url in subitems %}
{{ _self.menuItem(name, url) }}
{% endfor %}
</ul>
{% endif %}
</li>
{% endspaceless %}
{% endmacro %}
just add this code somewhere in your twig file (not in a {% block %}
thing!)
You then can call it like this for a single item:
{{ _self.menuItem('FooBar', path('foo_foobar')) }}
or for a item with subitems:
{{ _self.menuItem('FooBar', path('foo_foobar'), {
'Foo': path('foo_baz', {slug: 'foo'}),
"Bar": path('foo_baz', {slug: 'bar'}),
}) }}
Beautiful, isn't it?