TIOBE index is considered for some as the ultimate tool to guess wich language is the best, and they all claim to be in, I have a very different point of view about that.
Let define what TIOBE is:
"The index covers searches in Google, Google Blogs, MSN, Yahoo!, Baidu, Wikipedia and YouTube. The index is updated once a month." -- Wikipedia
Stop the lie, this is just a keyword statistic. Nothing to do with a real practice in software ingeneering.
My language is the best one!
Well, I guess not, because no language is universal, we use the tools needed to
interact with the softwares we need. As far as I know, to interact with a web
WordPress, PHP + MySQL are the server side saftest way to work with.
Telling one and only one language is the best one is definitively not serious.
How could I determine wich language I may use?
If you're asking, that mean you are not professionnal, you just have to choose the one wich provides a fast enought design and result to reach your goals, many languages can be used to reach these goals, and a project is almost made of code from more than one language.
Will the language I use survive?
Be straight: NO.
Delphi, Visual Basic, COBOL... so many graves. With time every language gets its grave, a language depends on the final targeted system. The systems change with time. Apple released swift recently, Android claims to use Kotlin... Nobody can really guess the futur.
An alternative more serious to TIOBE is the annual report from Jetbrains.
Unlike TIOBE, Jetbrains use a real survey to worldwide developers, that cost more money to do than a stat on keywords, it doesn't define the best and only one language you should learn or use. It provides the actual language used by developers for specifics projects and which they aim to learn for the same kind of projects (ie: Web Frontend, Desktop for linux or Windows...).
Please, don't repeat stupid things such as "Python will rule the World" because you read that on internet. Be smart, use you brain and don't forget: a project is more than a programming language.