How do you use C or C++ or Java for web scripting, to replace languages like PHP?

You can use C,C++ as a backend.You can associate same codebase in business-logic layer via web services or other APIs. Facebook uses php as front-end and C,C++ as backend. The downside is that time to market is much longer and it is much harder to get programmers up to speed with the system and introduce new features and all the coders have to work in A1 grade. So it is important to follow rule of "He who iterates fastest wins" is one of the reasons why people uses PHP instead of JAVA or C,C++ for web development.

There are few company use c/c++ as pure web logic layer, they change a lot  Especially nowadays. We iterate quickly, develop speed matters. We use dynamic languages instead, it's PHP. Back to topic. We used to use c++ to write web pages. For simpilicity. Web pages are just streams of output upon TCP, so it's not that different to write a command line programm and web application. HTTP protocol have detailed standard about it. In short you command line tools read and write to stdin/stout. Web page programm read request from socket between user and your server,response by write to it. So languages just doesn't make it different. Practically, we always use a standalone we server to handle user requests, then forward it to the real application. Between your we server there might some other protocol except http,eg, fast cgi,cgi.   If you use cgi,you could write web application in command line tools(so any language fits you).but the performance sucks.

I think that Facebook and Google use C++ and other languages in the backend. Possibly to query the database for more speed.  In php there is a function exec() which can be used to run command line.  You could possibly use this to run C++ or Java code

Remember that the C and C++ used in large sites may be far removed from the request handling/CGI code, and actually called indirectly from (say) a PHP or Python front-end, in the form of library, job/cache/search/database server, etc. If you want to use C++ for the front-end, there is Wt: http://www.webtoolkit.eu/wt

I know facebook wrote HipHop for PHP that compiles into C++ for their backend. https://github.com/facebook/hiphop-php/wiki/

There is Web Framework name wt(http://www.webtoolkit.eu/wt) Which is like Qt Framework. its easy and Quite cool. But i don't know it can be used in production environment.