private function _echo() {
    $node = new EchoStatementNode();
    $this->mustMatch(T_ECHO, $node);
    $expressions = new CommaListNode();
    do {
      $expressions->addChild($this->expr());
    } while ($this->tryMatch(',', $expressions));
    $node->addChild($expressions, 'expressions');
    $this->endStatement($node);
    return $node;
  }