$f = "carpal_tunnel_syndrome_inducing_function_name";
$a = $f($a);
$b = $f($b);

foreach (array(1,2,3) as $x) foreach (array(1,2,3) as $y) {
    ${"c_".$x."_".$y} = htmlspecialchars($_POST['c'][$x][$y]);
}