The basics of software are machine instructions that are sent to the computer processor so that the computer can perform computations, store data, and display media and information.
Another note is that some websites use more than one server-side language, maybe for transition ( such as Ameba.jp , a Japanese blog site ), or which uses only one ( Facebook which uses only PHP, or LinkedIn, which only uses Java )
Below is the basic list on where this area is under in the Website architecture.
[O] Front-end code -> CSS, HTML, JS
[/] Back-end code -> PHP, Java, C#, Ruby
[O] Database -> Oracle, MySQL, MongoDB
[O] OS -> Linux, Solaris, Windows
A very important thing to consider on the selection of a Server-Side language is Performance, Quick setup and development, Maintenance, and the most important factor is the Availability and talent pool of developers.
Top Server-Side languages for Websites
PHP is on the top of the list. according to w3techs.com, PHP powers 81% of all internet websites ( as of July 2015 ). All other languages do not come close. According to this report, PHP is used by most medium traffic sites, where these sites composes 80% of the internet. PHP is highly used in Social Media sites ( ex. Facebook and etc. ) Blogs ( ex. WordPress ) and Wiki sites. Theses sites are the internet platform used by most people.
PHP is described to be “the quickest web development language to learn and setup” and is preferred by most freelance and start-up developers. It is open source, with crude and simple scripting.
Here’s the official PHP page: https://secure.php.net/
Java programming language is popular among e-commerce and corporate websites, although it only comes to third with only 3% of all internet traffic ( ASP.net takes second place ). but according to this report, Java is in a steady rise, while PHP is on a steady decline. Although both languages have the same capabilities, Java may win on the performance since its compiled code, unlike PHP or Ruby.
Java is also open source and is integrated with J2EE technology and other 3rd party software such as Hibernate and Spring to become a full-tier webserver.
Recently, J2EE has become too large and complicated, with much maitenance overhead. Even the Struts framework has become outdated. There’s a new Play framework ( derived from Scala ) which eliminates all the complications of the J2EE architecture, but this is yet a rising technology and still on its semi-experimental stage.
On personal opinion, I am closely following Play framework, and just recently, Java creator James Gosling is already a consultant for Typesafe Inc. , the creator of Scala and Play framework ( according to Wikipedia.com ).
3.) C# and .NET
This comes as the second most-popular server-side programming language at 16.7% ( As of July 2015 ). C# and ASP.net are created and maintained from single vendor which is Microsoft Inc. The ASP.net comes as one package for Website development. C# is still in demand with several websites that are tied-up with this technology. A single vendor has an advantage over integration and a single contact point, but it offers less flexibility and vendor lock dependency, which most software firms avoid.
On the bright side, C# basic code has a very similar syntax to Java, so the switch has a lesser learning curve.
some links on C# and ASP.net tutorials
4.) Ruby on Rails / Node.js / Perl and other languages
Websites and links that show why Ruby is abandoned.