This is mainly intended for complex configurations to ease the work you
have with normalizing different configuration formats (YAML, XML, and PHP).
First, you have to set-up a config tree:
$treeBuilder = new TreeBuilder();
$tree = $treeBuilder
->root('security_config', 'array')
->node('access_denied_url', 'scalar')->end()
->normalize('encoder')
->node('encoders', 'array')
->key('class')
->prototype('array')
->before()->ifString()->then(function($v) { return array('algorithm' => $v); })->end()
->node('algorithm', 'scalar')->end()
->node('encode_as_base64', 'scalar')->end()
->node('iterations', 'scalar')->end()
->end()
->end()
->end()
->buildTree()
;
This tree and the metadata attached to the different nodes is then used
to intelligently transform the passed config array:
$normalizedConfig = $tree->normalize($config);
