PHP block

Hello,
i am trying to use something like:

<?php
$browserlang = $_SERVER['HTTP_ACCEPT_LANGUAGE'];
$lang = $browserlang[0] . $browserlang[1] . $browserlang[2] . $browserlang[3] . $browserlang[4];

if (($lang=="sk_SK") OR ($lang=="sk-SK")) {
    header("Location: https://www.example.sk/sk");
}
else if (($lang=="en_EN") OR ($lang=="en-EN") OR ($lang=="en_GB") OR ($lang=="en_US") OR ($lang=="en-GB") OR ($lang=="en-US"))  {
    header("Location: https://www.example.sk/en");
}
else {
    header("Location: https://www.example.sk/en");
}

?>

in a block but wont work, the php option is highlighted and the code is working if i test with ‘my custom function’ plugin which use php code.

Is there a special syntax i must use for php to be run in AIPro block?

Thanks