The provided namespace can be either a single namespace or
an array of namespaces, as strings. The identifier/alias is
always a single, alpha-numeric ASCII string.
Calling this method multiple times with different PHP namespaces
for the same alias causes that namespace to be *extended*,
meaning that the PHP namespace you provide second, third etc.
are also used in lookups and are used *first*, so that if any
of the namespaces you add contains a class placed and named the
same way as one that exists in an earlier namespace, then your
class gets used instead of the earlier one.
Example:
$resolver->addNamespace('my', 'My\Package\ViewHelpers');
Any ViewHelpers under this namespace can now be accessed using for example {my:example()}
Now, assuming you also have an ExampleViewHelper class in a different
namespace and wish to make that ExampleViewHelper override the other:
$resolver->addNamespace('my', 'My\OtherPackage\ViewHelpers');
Now, since ExampleViewHelper exists in both places but the
My\OtherPackage\ViewHelpers namespace was added *last*, Fluid
will find and use My\OtherPackage\ViewHelpers\ExampleViewHelper.
Alternatively, setNamespaces() can be used to reset and redefine
all previously added namespaces - which is great for cases where
you need to remove or replace previously added namespaces. Be aware
that setNamespaces() also removes the default "f" namespace, so
when you use this method you should always include the "f" namespace.
