I'd go with gogodr's solution, it'll be the simplest for you - BUT ONLY IF you just request public ticker data, you should in NO CASE send private user-data (passwords ect...) through 3rd-party proxy-services.
If you want to read more about JSONP and how to evade the cross-domain issue for JSON-requests, you can take a look here:
http://en.wikipedia.org/wiki/JSONP (or google for JSONP)
Thanks to gogodr, that should work just fine, and of course I'll only be using it for non-private information.
The only other thing to be careful of is that you're now putting yourself in the hands of whateverorigin: they could send back false or even malicious data. Not that I have any reason to suspect that they would, but it's just something to think about.
If you whant to make a site that would display API data from multiple exchanges and display it to the user use php better!
He could still be using PHP; he just wants the client to load the information instead of doing it on the server.