How many languages must I learn?

When I started this project, it seemed like the LAMP stack of applications was the best solution, but it's not the only one. Since I'm new to programming, I don't have a preference for any language, and I carry no bias for one or another, so it's important to me to spend enough time choosing the right one for the job. Right now it looks like I have to learn

• SQL (Structured Query Languange) for MySQL, the database application.
• PHP (Php: Hyertext Pre-processor) to communicate with that database
• HTML (HyperText Markup Language) to correctly mark up the content of the finished web pages
• CSS (Cascadding Style Sheets) to control the design of the finished HTML pages
• JavaScript to provide client-side scripting and to make use of AJAX
• XML (eXtensible Markup Language) to move data from the database to the web page

What a job. HTML is the easiest (it's not even a language, just markup), but the others will require diligence and study.