Does Scope-Resolution Operator Always Follow 'parent'?

Hello everyone, I have a question about the parent keyword: is there any valid situation where it can appear without the :: operator following? I am asking to fix a bug in php-mode[1] for GNU Emacs. Consider the following code:

    echo $parent;
    echo parent::$foo;
    echo $this->parent;

The mode incorrectly highlights parent in the final line as if it were the keyword, but PHP itself treats it as a member of an object. My idea for fixing this incorrect syntax highlighting is to only treat parent as a keyword if the :: operator follows it. But I want to make sure that this assumption is correct. Thanks in advanced for any help! [1]: https://github.com/ejmr/php-mode -- ejmr 南無妙法蓮華經