No, it's much much older than PHP. It's in PHP because it was in Perl (which is also why it's in Ruby). I think iit was in Perl because it was in sh. But I wouldn't be surprised to hear that it's older than that. Snobol maybe?
Sure, but "I like it" is actually a good reason. You can dissect I like it into maybe that I find it more productive, that I find strings easier to read when they're like that, or for other reasons, but it actually boils down to aesthetics: I like it :)