Techniques for writing a scalable website

Question

I am new in the website scalability realm. Can you suggest to me some the techniques for making a website scalable to a large number of users?

Answer 1

Very similar: How Is PHP Done the Right Way?

Scalability is no small subject and certainly more material than can be reasonably covered in a single question.

For instance, with some kinds of applications, joins (in SQL) don't scale, which brings up all sorts of caching and sharding strategies.

Beanstalk is another scalability and performance tool in high-performance PHP sites. As is memcache (different kind).