src/Extension/LogConfiguration.php
public function getConfigTreeBuilder()
    {
        $treeBuilder = new TreeBuilder();
        $rootNode = $treeBuilder->root('logging');

        $rootNode
            ->children()
                ->arrayNode('channels')
                    ->useAttributeAsKey('name')
                    ->prototype('array')
                        ->addDefaultsIfNotSet()
                        ->children()
                            ->scalarNode('handler')
                                ->isRequired()
                                ->validate()
                                    ->ifNotInArray(array('stream', 'error_log'))
                                    ->thenInvalid('Invalid logging handler %s')
                                ->end()
                            ->end()
                            ->scalarNode('level')->defaultValue(200)->end()
                            ->arrayNode('options')->defaultValue(array())
                                ->prototype('scalar')
                            ->end()
                        ->end()
                    ->end()
                ->end()
            ->end();

        return $treeBuilder;
    }
public function getConfigTreeBuilder()
    {
        $treeBuilder = new TreeBuilder();
        $rootNode = $treeBuilder->root('logging');

        $rootNode
            ->children()
                ->arrayNode('channels')
                    ->useAttributeAsKey('name')
                    ->prototype('array')
                        ->addDefaultsIfNotSet()
                        ->children()
                            ->scalarNode('handler')
                                ->isRequired()
                                ->validate()
                                    ->ifNotInArray(array('stream', 'error_log'))
                                    ->thenInvalid('Invalid logging handler %s')
                                ->end()
                            ->end()
                            ->scalarNode('level')->defaultValue(200)->end()
                            ->arrayNode('options')->defaultValue(array())
                                ->prototype('scalar')
                            ->end()
                        ->end()
                    ->end()
                ->end()
            ->end();

        return $treeBuilder;
    }
Generates the configuration tree builder.

@return \Symfony\Component\Config\Definition\Builder\TreeBuilder The tree builder