LifeinAsia - 4:20 pm on Apr 12, 2011 (gmt 0)

Yes, both (three, as PHP is a programming language and MySQL is a database) together. It gives you a serious leg up on the programmers who don't know SEO (a lot) and SEO "experts" who don't know programming (and/or databases). Being able to integrate all three aspects makes you much more valuable than someone who has to outsource the other aspects.