#6 PHP / MySQL

PHP is a server-side scripting language designed for web development but also used as a general-purpose programming language. PHP is now installed on more than 244 million websites and 2.1 million web servers.

MySQL is the world's most widely used open source relational database management system (RDBMS) that runs as a server providing multi-user access to a number of databases. The SQL phrase stands for Structured Query Language

The open source scripting language runs on more than 20 million websites and powers high-profile sites we deal with every day, including Facebook, Wikipedia, Wordpress or Drupal. So you can say that it’s all over web.

PHP is currently ranked as the most sought-after skill on Elance, with MySQL and Wordpress also cracking the top ten. There are more than a quarter of a million PHP programming gigs listed on Elance, a global online staffing platform, alone.

Read more: 10 Most Amazing Technologies Set To Rule The World  , Warren Buffett Joins Twitter; 1000 Followers Per Minute