As a language PHP has some problems. That is not to say that it is a bad language. I use PHP with CodeIgniter or Kohana (frameworks) on a regular basis.
That said, I believe that Ruby and Python are both more robust languages on the whole. I suggest doing some generic (read: non-web) scripting in the languages and see what feels right, including community, documentation, and libraries.
One thing i've always had to consider is what servers actually support Ruby. A few personal projects i've made in Ruby. However, when working on Web applications for other people (Who already have a server), they may not support Ruby (Or PHP for that matter).
I think it really comes down to preference. I learnt PHP first off, then discovered the power of Ruby.
the support of the server is not my concern though it can be considered as one criteria + I don't have any preference or feelings about any framework!
So suppose I have an Idea and I'm searching to find out my co-founder who is a developer. shall I go for php developer or ruby? what are the elements which i should consider? and how this choice will effect me as the CEO in the future? for example is it hard to find a ruby developer or PHP? etc....
The answer to that: Don't pick them based on the language they are proficient with. If you find an incredibly sage person who writes webapps in COBOL, take them. The language is not going to dictate the success of your venture.
As for numbers, there are generally more PHP developers than Ruby developers, but you want a good developer, not just a developer.
According to what I have heardÖ finding a good PHP developer is much more easier than finding a ROR developer coz ruby is new and less developers available and they demand higher salary.
So my last line up there had perhaps some unclear meaning. There are more PHP developers out there, but there are good developers to be had in both arenas. As for salaries, you get what you pay for.
That said, I believe that Ruby and Python are both more robust languages on the whole. I suggest doing some generic (read: non-web) scripting in the languages and see what feels right, including community, documentation, and libraries.
Good read: http://www.codinghorror.com/blog/archives/001119.html