A Little Advice Concerning Server Side Issue

I am developing a chat application that is going to be used by thousands of users. I am stacked concerning the technology to use on the server side. I wanted to write the application in PHP. The application will work more or less like some of the subscription chat applications like :: Olark, Zopim, etc..

Initially i wanted to use MySQL database for the chatting between users.

But i came across a post that someone wrote a chat application using database but some users in the post commented that using database is very very bad. One person suggested using XMPP. He suggested ijabbar using existing XMPP protocol and to do it with ejabberd or openfire as jabber server. I was thinking that XMPP is for Instant Messaging and not for normal chatting applications. May be am wrong :-)

I have also came across some posts talking about NodeJS.

At the moment am very confuse what to use on the server side. Am willing to learn any technology to make the application more efficient and scalable.

Am asking if you guys can help me out with some suggestions so that i can make the right decision.

Thanks for your help.

PS Moderators:

My aim for asking this question is for others to help me to make some decisions because i don't know what to do now. My question is not intended to incite argument. I just need someone to advice me the right way to go. I am just saying it because i have seen some people's posts closed. Thank you.