Linking PHP with local C++ program - php

Question

I've been looking into this for several hours, but everything I've looked at seems rather daunting. I've been using PHP for all of the simple stuff on my website so far. I'm doing a lot of statistical work, and I would like to have c++ available for the more intense calculations.
The c++ would be running locally on the same Unix machine as PHP.
Something like the following is what I'm at a loss for how to do:
<?php
//c++ program has a counter initialized to 0
//PHP tells c++ to add 5 to the counter. $incremented is 5
$incremented = increment_in_cpp_and_return(5);
//$incremented_again will be 7
$incremented_again = increment_in_cpp_and_return(2);
?>
Of course, I'm running some monte-carlo simulations and traversing really big trees instead of incrementing numbers, but that's not what's holding me back.
C++ just needs to listen for a number and return another number (maybe some stuff in JSON at most). It is important for the c++ to keep track of its variables between calls.
I've done a lot of reading on TCP, socket programming, etc and I'm just a little doubtful that this as complicated as the examples make it out to be. A lot of things have pointed me to this https://beej.us/guide/bgnet/html/multi/clientserver.html#simpleserver
If it really is more than 100 lines of c++, are there some popular libraries, or is there a simple implementation in another language?
Thanks!

Answer 1

If you only want to access your C++ program from PHP (or use PHP as the web frontend for your C++ code), an alternative to communicating over a socket would be to embed the C++ code into PHP as an extension.
There's a fair amount of boilerplate code associated with it, but most of it is generated for you by the ext_skel script (included in the PHP source).
Most information online about writing PHP extensions relates to using C, see Extending PHP with C++? for a couple of gotchas related to using C++ for this.

Answer 2

If your C++ is executeable, you could open it as a program, pass data to it via STDIN and pass the return value back to PHP via STDOUT. See proc_open­Docs.
Your standard C++ library should offer access to STDIN and STDOUT, so you already have what you need.
I'm a little confused about how the c++ keeps its state between calls. Can proc_open be used to pass via STDIN to a c++ program that is continuously running? I'm worried that it starts a new instance of the c++
You might be looking for a Named pipe­Wikipedia, a form of inter-process communication (see as well: What are named pipes?), that is supported by most operating systems. It's simple I/O (FIFO) and similar compared to STDIN and STDOUT. You can keep your executable in memory while the other processes can send data to it.
Another simple way is to use sockets, those are supported by PHP as well and should be with your C/C++. Sockets will work across different machines, so you can run your (memory/CPU intensive?) own executable on a dedicated server that does only the calculation for example. Just looks what suits better in your case, from the comment I read you're looking for interprocess communication.
posix_mkfifo­Docs (including sample PHP code in user-notes)
Sockets Tutorial - a simple tutorial on using sockets for interprocess communication (Linux Howtos)
Introduction to Named Pipes (Linux Journal)
Introduction to Interprocess Communication Using Named Pipes (Sun Developer Network)
(these are just some resources, you naturally can find more with a little research, I think for both named pipes and sockets you should be able to find source-code examples for your case)

Answer 3

You could try:
exec()
You send the data from PHP as arguments for the C++ written program that will be executed and the program will return the output so you can use it in PHP after the C++ program's execution.

Answer 4

I've been using gSOAP for remote procedure calls between C++ and PHP, and if you're using PHP5, the interaction is made very easy; see http://www.php.net/manual/en/class.soapclient.php