Suppose I want to build a server for the university's academic interests. The server is dedicated only to a site, where users (students and lecturers) just view and fill the academic data. But at a time (e.g. once a semester), about 12,000 students will access the site simultaneously. Due to limitation of resources, I have to build the server using free software (except for the operating system Windows 7, the university has been prepared). The hardware is also limited to the usual 4-core computers (eg, Ivy Bridge Intel Core i7-3770) with approximately 16GB of memory (DDR3 1600 MHz), equipped with an RJ-45 port (Intel 82 579 Gigabit Ethernet). With all these limitations, I have to choose the software (web server, database, etc) are appropriate for this purpose is achieved. I decided to create a site in PHP. Please help me by answering the following questions based on your expertise. (my prime candidate software to consider after googling)

1. Web server which is faster & stable & secure, when implemented and optimized for PHP? And why? (nginx)
2. PHP accelerator which is faster & stable & compatible with the selected web server? And why? (APC with Zend Optimizer+)
3. Database which is faster & stable & secure, when implemented and optimized for selected web server and selected PHP accelerator? (MySQL)
4. Are there any errors that have been or will be happening from my condition is? If there is, please enlighten me?
5. Is there anything else I need to know in order to achieve this goal? If there is, please enlighten me?

I understand that the performance also depends on the implementation of source-code program, so I assume it will create a site with the best efficiency (e.g. using AJAX).