Is the speed of PHP Sockets good enough for a chat server?

[bnashenas1984]

Hi everyone
i'v built a website which might have thousands of visitors per day.
I also have some kind of one way chatbox which works with PHP socket and Flash (AS3).

At least 350 users are going to be connected to the chatbox at the same time to receive info from the admin. Information sent by the socket is very important so we shouldn't have any data loss.

I'm going to have a dedicated server for this.

So my question is :
Is PHP socket fast enough for this job? Doesn't it slow down the server ?

Thanks/ Behzad