Zhiyong Ma said:(1) Does PHP support some kind of dynamic refresh of web pages to remind the administrator some data from mysql has been changed and what their new value is . One simplest example maybe just like a forum page automaticlly tells its online user how many people is online? Of couse, this can be fulfilled by just refresh the pages by hand, but it is not recommended.
Zhiyong Ma said:(2) Does PHP or apache have enough security technology to ensure remote control through a web server?
Yes. If you have a need for truly secure site (if, for example, you need to transfer sensitive data like credit card numbers or SSNs), you'll want to look into SSL (Secure Sockets Layer) for encryption between the client and the server. Try Apache-SSL or mod_ssl for starters. For the record, Apache is usually considered, with or without SSL, to have security far superior to Microsoft's ISS, though in both cases it's of tantamount importance to keep your security patches up to date.
I'm not an expert in PHP or JSP security, but I do know that the two biggest security factors on either (or any, really) platform are script integrity and patches. Script integrity means, essentially, that your scripts are written from day 1 with security in mind. This cannot be explained in a terse manner, so I recommend you do lots and lots of reading on secure scripting. Patches, as above, are essential to any enviroment that requires any security. Most of these technologies have associated newsletters, and I suggest that you subscribe to them so that you can have up-to-the-minute knowledge of new security patches that have been issued. I consider PHP to be secure, and I recommend it. You are, of course, on a PHP forum.
Zhiyong Ma said:(3) Does PHP script have some way to communicate with my main control process which is running in the server? The source code for my main control process will be in C language. One solution that I found is to use pipe file. But I am not sure. And are there other ways?
Again, I'm not an expert in this area, so I'll leave it up to another poster to answer more completely, but I assure you that PHP ships with support for many libraries and APIs as well as standard program execution functions, so I don't think you'll find it at all lacking in that department. I recommend that you browse the function reference to get a better idea of PHP's process interoperability support.