Compiles the node to PHP.
Twig_Compiler A Twig_Compiler instance:
Overrides Twig_Node::compile
public function compile(Twig_Compiler $compiler) {
$name = $this
->getAttribute('name');
$compiler
->addDebugInfo($this)
->write('if (isset($context[')
->string($name)
->raw('])) { $_')
->raw($name)
->raw('_ = $context[')
->repr($name)
->raw(']; } else { $_')
->raw($name)
->raw("_ = null; }\n");
}