I've been toying with Ruby for a couple of months now. PHP is definitely more mature as a web scripting language, but that's mainly due to its age relative to Ruby.
Ruby's strongest points are an excellent object model, truly object oriented not bolted on. It does this in ways that PHP will never be able to, sadly. A simple example would be the following code.
5.times do |num| puts num.to_s end
Which would yield the output
1
2
3
4
This is by no means the most elegant example, but it's a simple example to show how clean the syntax, and object model is. Notice how the constant number is even an object.
Ruby has a long ways to go before it becomes a great web scripting language, but I have no doubt that it will get there, the ruby community is extremely intelligent and motivated.
So for those of you who have thus far discounted it, look out, it's coming, and it's real 😉