Customize Interface Template

Hi, I’m making progress with the implementation of the Patreon plugin on my website.

Now I’d like to edit the default interface.

If I do, for example:

$tier = 10;
echo Patreon_Frontend::displayPatreonCampaignBanner(
  $tier,
    array(
      'direct_unlock'=> $tier,
      'redirect' => $redir
    )
);

And, in functions:

function edit_patreon_template( $patreon_level, $args ) {
  echo $patreon_level;   // Just to see the output
  echo '<br>';                  // Just to see the output
  var_dump($args);        // Just to see the output
  echo '<br>';                  // Just to see the output
  return 'Hey, you must be logged in!';
}
add_filter( 'ptrn/override_interface_template', 'edit_patreon_template', 10, 2 );

I get this output, instead of ‘Hey, you must be logged in!’:

What am I doing wrong?
Thank you

You may be missing one or two <?php ?> tags in your code, which seems to cause the earlier function you are using (Patreon_Frontend::displayPatreonCampaignBanner) to be displayed as html instead of being interpreted as PHP code.