Php combineret med XHTML need answer !

hello to all oF U,

I have just start learning PHP and me is not good in php. I have a gueation to all of U that how can i cambine php with xhtml??
I know its a simple for U but its not for Me.

$number = 7;

if($number > 5) {
  echo("Passed");
} else {
  echo("Failed");
}

thats the answer of a question but i need a test box and a button which i can do with use tag <form> and input but How to do that in PHP.
PLease answer me i need a big help !plzz answer myy ques.
thanks in advance.