Hi ,
I am in a bit of a dilema , I know XHTML 1.0 really well and HTML really well. But what Mark Up Language should I use in my latest php application XHTML 1.0 or HTML 5 ?
Also which would be future proof ?
And finally if I was to build a normal site what Langauge would be best to use now ?
XHTML is nice, but it's really only practical as the output of some sort of XML-based process. Stick to HTML 5 for now.
You should stay with XHTML. HTML5 is cool but not yet fully supported by recent browsers. I believe that it will take a couple of years to fully adopt HTML5. HTML5 is not understood by quite-recent browsers and we know that (unfortunately) there are lots of users around the world that do not upgrade their software. Additionally, HTML5 is not supported by most of mobile browsers. Of course you could go with HTML5 by thinking in terms of future proof, but you are going to loose a considerable amount of market share today.
For the time being, I would advise you to stick to HTML 4 (and not XHTML).
As mentioned, if HTML5 is the future way to go, it is not supported enough for now.
Regarding XHTML vs HTML, this is a bit a trollish subject, but I do agree with Jeff Atwood and James Bennet that XHTML is just not worth its pain.
Stick to HTML 4.
In most cases, generating HTML Compatible XHTML is more trouble than it is worth, while HTML 5 is still subject to change and the new features in it are poorly supported.