PHP - Multiple (a lot) if (isset) checks - Is there a short way

Question

I have a page that takes a lot of $_GET parameters but it's not always guaranteed for all fo them to be used. So i get a lot of warnings right now for undefined variables. I obvously need to check if it's set with isset so i avoid warnings but i have literally 80!!!

Just showing few for example (but they are much more than that, maybe 80)

$pt2r2c1 = htmlspecialchars($_GET['pt2r2c1']);
$pt2r2c2 = htmlspecialchars($_GET['pt2r2c2']);
$pt2r2c3 = htmlspecialchars($_GET['pt2r2c3']);
$pt2r3c1 = htmlspecialchars($_GET['pt2r3c1']);
$pt2r3c2 = htmlspecialchars($_GET['pt2r3c2']);
$pt2r3c3 = htmlspecialchars($_GET['pt2r3c3']);
$pt2r4c1 = htmlspecialchars($_GET['pt2r4c1']);
$pt2r4c2 = htmlspecialchars($_GET['pt2r4c2']);
$pt2r4c3 = htmlspecialchars($_GET['pt2r4c3']);
$pt2r5c1 = htmlspecialchars($_GET['pt2r5c1']);
$pt2r5c2 = htmlspecialchars($_GET['pt2r5c2']);

So i started doing this manually ... but at the 40th i felt stupid and i thought if there is a better way to do it.

if (isset($_GET['pt1r5c3'])) {
$pt1r5c3 = htmlspecialchars($_GET['pt1r5c3']);
}
if (isset($_GET['pt1r6c1'])) {
$pt1r6c1 = htmlspecialchars($_GET['pt1r6c1']);
}
if (isset($_GET['pt1r6c2'])) {
$pt1r6c2 = htmlspecialchars($_GET['pt1r6c2']);
}
if (isset($_GET['pt1r6c3'])) {
$pt1r6c3 = htmlspecialchars($_GET['pt1r6c3']);
}
if (isset($_GET['pt2r1c1'])) {
$pt2r1c1 = htmlspecialchars($_GET['pt2r1c1']);
}
if (isset($_GET['pt2r1c2'])) {
$pt2r1c2 = htmlspecialchars($_GET['pt2r1c2']);
}
if (isset($_GET['pt2r1c3'])) {
$pt2r1c3 = htmlspecialchars($_GET['pt2r1c3']);
}

Answer 1

Ok thanks to some hints in the comments i realised i can just try with a simple array and foreach. So after some trial and error i managed to do it that way. Hope it help others.

   $tree_variables_array = ['pt1r1c1', 'pt1r1c2', 'pt1r1c3', 'pt1r2c1'];
        
        
    foreach ($tree_variables_array as $var) {
      if(isset($_GET[$var])) {
        $$var = htmlspecialchars($_GET[$var]);
      }
    }