PHP Question

So,
I coded a HTML/CSS pricing table into an upgrade page.

I need to add a bit of PHP to the buttons but not sure how to go about it.
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I basically wanna add something like {if user is not in group show <div class="blah">BUY</div> else if user is in group show <div class="blah">ALREADY UPGRADED</div>}
and so on ..

I can figure out the rest on where to add it.
Somebody lead me in the right direction, please :noh: