If you want to upgrade php mysql and apache to higher versions than gardo has in his repositories ... you'll need to manually update those packages. This is not a Vicidial question (and likely to cause ... problems, LOL).
Perhaps if you shared the Reason you feel the urge to upgrade, we could be of assistance in that regard, but if all you want is to upgrade some packages that is purely a question for the OS forum and/or the forum for each of the packages in question.
Ordinarily upgrading packages is fairly straightforward, but only if you approach it in a straighforward manner. For example: If you want to upgrade mysql in CentOS, doing so according to instructions for CentOS or MySQL will likely result in success.
However, doing so according to instructions for an application suite that is actually using an earlier version of mysql, and outside that application suite's normal metodology, seems likely to be counterproductive. Just my opinion.
Best bet: Google "upgrade Mysql in Centos to 5.6".
Not to say Gardo won't jump on here with instructions in 5 minutes (detailed ones, at that) as he is a bit of a CentOS God ... but I wouldn't hold my breath (I also wouldn't assume that he didn't just execute the aforementioned google search and paste the results ...
)