exec( <<setRootNode( $root = $tree->createNode( 'Metals', array() ) ); $root->addChild( $tree->createNode( 'Fe', array( 'melting_temp_K' => 1811, 'boiling_temp_K' => 3134 ) ) ); // Fetch data var_dump( $tree->fetchNodeById( 'Fe' )->data ); ?>