interaction with PHP and c/c++ would be possible. But your question doesn't such clear to me. I don't think you need to include php with C++. rather you need to call C++'s function from PHP, right?
And if you want to call PHP's function from C++, Make something like Webservice. Where you will call a URl with specific parameter and it will return your result. Doesn't need to know weather you use PHP or Asp or JSp.
Anyways different situation need different technique. Obviously there have some limitation. These will depend on your requirements.
Find the PHP_and_C.pdf file from http://tech.groups.yahoo.com/group/phpresource/files/
Hope this helps.