I am a PHP and PERL coder and lately I have started feeling that things would have been little easier had I chosen Python or Ruby as the language for implementation, more so when I think of scalability.
I know about 60% of all web application are still written in PHP and includes biggies like Yahoo and Facebook. But still I would like to know whats the general perception now.
Should I learn one of the newer languages or continue using PHP as a language of choice for web applications.
Until you start having problems with the current technology you are using, I see no reason to switch to a new one.
I would however advocate changing languages every once in a while for educational purposes.
A good rule of thumb is to use the technology that suits the application. i.e.: don't use Python just for the sake of using Python...use it when you have a reason to use it. If you need better OOP support, more libraries, then Python is just fine. The trade-off in your case is the learning curve.
Q1: Should I learn another language?
A1: Definitely. no if's, why's or but's. Always learn.
Q2: Should I move working applications to another language?
A2: Don't break what's working; but if they're not working well, then rewriting might be a good idea.
Q3: Are Python/Ruby/Scala more 'scalable' than PHP?
A3: Not really; but there seem to be fewer bad frameworks, so it might be easier to find the good ones.
I haven't heard scalability as one of the reasons for choosing Ruby/Rails. More often people say that development (including modifying an existing app) and debugging are faster.
Specifically for scalability, I don't see what Python or Ruby do that can't be done (relatively) easily in PHP.
The scalability issues in web applications are most of the time language-independant, so the solution to these problems will be available in any language. Of course the ease and efficiency of the implementation will vary, but PHP isn't the worse in both ease and efficiency.
I'd stick with PHP, as long as the reason to switch to a new language is to gain more scalability. But if the reason becomes something like "I feel I have nothing left to learn in PHP and I would like to learn a new language", then go ahead ! :)
If you are looking for scalable then switching to Python will really be a good choice. I was once a PHP developer and developed around 150 applications for a telecom company. Slowly slowly i realized that i need a something which can glue with other programming language for scalability and my answer was Python. I really had great success with Python. The best thing about Python is that it is not just a scripting language its more than that. You will find out once you start working in Python.