I want PHP notification to exe a URL, let exe after the operation to return a string to PHP

I want PHP notification to the EXE a URL, let exe after the operation to return a string to PHP

Process
When the customer browses the Web page, I enter a URL, I use Ajax to notify EXE this URL, and then return a corresponding string to the client is browsing the page.
The client confirms this string on the Web page.

I'm not sure how to use PHP to notify the EXE string.
EXE callback information to PHP and in what way better.

Note: The Web server is Linux, which means that EXE and the Web server are not a host computer.
------to solve the idea----------------------
EXE and Web server are not a single host
So EXE should have a Web server on the machine, and the EXE should work in CGI mode
can be accessed using file mode, curl, sock

If it is on the same machine, it can be called with the system function (note permissions)

EXE can only output data to standard output, otherwise PHP cannot receive

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