How can I use C++ code to interact with PHP?

Well you have not defined what you are trying to do, but if you need to the C++ interface, then look at the ext directory in the source code to understand how to write a PHP extension that you can then load and use from your PHP scripts.

A couple of links that may help:

http://www.devarticles.com/c/a/Cplusplus/Developing-Custom-PHP-Extensions-Part-1/ http://devzone.zend.com/article/1021

swig, the Simplified Wrapper and Interface Generator can help you wrapping (existing) c++ into a php module.

SWIG is a software development tool that connects programs written in C and C++ with a variety of high-level programming languages. SWIG is used with different types of languages including common scripting languages such as Perl, PHP, Python, Tcl and Ruby.

You can actually execute compiled applications without any sort of API:

$output = exec('/path/to/yourapp');

Beyond that, you could always write a PHP extension. There's a good guide on the subject here: http://devzone.zend.com/article/1021

You can add functions/classes to PHP, programmed in C (and you can wrap a C++ class from C, if I remember correctly from an article I read some time ago), which might allow you to do some things faster -- if programmed well : no need for interpretation of PHP code ; only execution of machine code, which is generally way faster.

To do that, you'll have to develop a PHP extension.

There are not that many resources available on the Internet about that, but these one might help you to start :

• Extension Writing Part I: Introduction to PHP and Zend
• Extension Writing Part II: Parameters, Arrays, and ZVALs
• Extension Writing Part III: Resources

And, specifically about the C++ part, this one might help too :

• Wrapping C++ Classes in a PHP Extension

If you are really interested by the subject, and ready to spend some money on it, you could also buy the book Extending and Embedding PHP (some pages are available as preview on Google Books too) ; I've seen a couple of times that it was the book to read when interested on this subject (In fact, I've bought it some time ago, and it's an interesting read)

By the way, the author of that book is also the author of the first four articles I linked to ;-)