PHP is not outdated, there is no real concensus on what is the most popular programming language out there, some people are obviously biased, some based it off number of job postings in which case PHP and possibly .NET are the top ones. It depends on what you are doing. See them as upgrades on each other.. not that they are bad, just depending on the workload you'll put it through.
With that said, there is no real answer to this either, it depends on who you can find, the number of resources you yourself can find on the language for help, feedback, etc.
Go to builtwith.com and it will tell you the stack any website is built upon including the framework and languages :)