: '';

  echo '<label class="screen-reader-text" for="ojo_confirmation_filter">Bestätigungsstatus filtern</label>';
  echo '<select name="ojo_confirmation_filter" id="ojo_confirmation_filter">';
  echo '<option value="">Alle Anmeldungen</option>';
  echo '<option value="unconfirmed" ' . selected($current, 'unconfirmed', false) . '>Noch nicht bestätigt</option>';
  echo '<option value="confirmed" ' . selected($current, 'confirmed', false) . '>Bestätigt</option>';
  echo '</select>';
});

// Auswahl des Filters auf die Datenbankabfrage anwenden
add_action('pre_get_posts', function ($query) {
  if (!is_admin() || !$query->is_main_query()) {
    return;
  }

  if ($query->get('post_type') !== 'ojo_registration') {
    return;
  }

  $filter = isset($_GET['ojo_confirmation_filter'])
    ? sanitize_key(wp_unslash($_GET['ojo_confirmation_filter']))
    : '';

  if ($filter === 'confirmed') {
    $query->set('meta_query', [
      [
        'key'     => 'confirmed',
        'value'   => '1',
        'compare' => '=',
      ],
    ]);
  } elseif ($filter === 'unconfirmed') {
    // Berücksichtigt auch ältere/ungewöhnliche Einträge, bei denen confirmed fehlt.
    $query->set('meta_query', [
      'relation' => 'OR',
      [
        'key'     => 'confirmed',
        'value'   => '0',
        'compare' => '=',
      ],
      [
        'key'     => 'confirmed',
        'compare' => 'NOT EXISTS',
      ],
    ]);
  }
});

// Vollständige Formulardaten auf der Detailseite einer Anmeldung anzeigen
add_action('add_meta_boxes_ojo_registration', function () {
  add_meta_box(
    'ojo_registration_details',
    'Ausgefüllte Anmeldedaten',
    'ojo_render_registration_details_metabox',
    'ojo_registration',
    'normal',
    'high'
  );
});

if (!function_exists('ojo_render_registration_details_metabox')) {
  function ojo_render_registration_details_metabox($post) {
    if (!current_user_can('edit_post', $post->ID)) {
      echo '<p>Du hast keine Berechtigung, diese Anmeldedaten anzusehen.</p>';
      return;
    }

    $fields = [
      'firstname'       => 'Vorname',
      'lastname'        => 'Nachname',
      'birthdate'       => 'Geburtsdatum',
      'email'           => 'E-Mail',
      'phone'           => 'Handynummer',
      'parent_phone'    => 'Telefonnummer Eltern',
      'address'         => 'Adresse',
      'zip'             => 'Postleitzahl',
      'city'            => 'Stadt',
      'region'          => 'Regierungsbezirk',
      'notes'           => 'Anmerkungen',
      'proben_einschr'  => 'Proben-Einschränkungen',
    ];

    echo '<table class="widefat striped" style="max-width:1000px;"><tbody>';
    foreach ($fields as $key => $label) {
      $value = get_post_meta($post->ID, $key, true);
      echo '<tr><th style="width:240px;">' . esc_html($label) . '</th><td>';
      echo $value !== '' ? nl2br(esc_html((string) $value)) : '–';
      echo '</td></tr>';
    }

    $instruments = get_post_meta($post->ID, 'instruments', true);
    echo '<tr><th>Instrumente</th><td>' .
      esc_html(is_array($instruments) ? implode(', ', $instruments) : (string) $instruments) .
      '</td></tr>';

    $checkboxes = [
      'agree_rules'             => 'Teilnahmebedingungen Arbeitsjahr',
      'optional_november_weekend' => 'Optionales Novemberwochenende',
      'vereinsbeitritt'         => 'Vereinsbeitritt / Satzung',
      'agree_photos'            => 'Foto- und Filmaufnahmen',
      'eltern_einverstaendnis'  => 'Einverständnis der Eltern',
      'data_consent'            => 'Datenspeicherung',
      'agree'                   => 'Anmeldebedingungen und Satzung gelesen',
    ];

    foreach ($checkboxes as $key => $label) {
      $value = get_post_meta($post->ID, $key, true);
      echo '<tr><th>' . esc_html($label) . '</th><td>' .
        ((string) $value === '1' ? '<strong>Ja</strong>' : 'Nein') .
        '</td></tr>';
    }

    $confirmed = (string) get_post_meta($post->ID, 'confirmed', true) === '1';
    echo '<tr><th>E-Mail-Bestätigung</th><td>' .
      ($confirmed ? '<strong style="color:#137333;">Bestätigt</strong>' : '<strong style="color:#b45309;">Noch nicht bestätigt</strong>') .
      '</td></tr>';

    $submitted = get_post_meta($post->ID, 'submitted_at', true);
    echo '<tr><th>Anmeldung eingegangen</th><td>' .
      ($submitted !== '' ? esc_html((string) $submitted) : '–') .
      '</td></tr>';

    $confirmed_at = get_post_meta($post->ID, 'confirmed_at', true);
    echo '<tr><th>Bestätigt am</th><td>' .
      ($confirmed_at !== '' ? esc_html((string) $confirmed_at) : '–') .
      '</td></tr>';

<br />
<b>Warning</b>:  Cannot modify header information - headers already sent by (output started at /homepages/35/d911442271/htdocs/clickandbuilds/OstbayerischesJugendorchester/wp-content/plugins/ojo-anmeldung/ojo-anmeldung.php:1) in <b>/homepages/35/d911442271/htdocs/clickandbuilds/OstbayerischesJugendorchester/wp-includes/sitemaps/class-wp-sitemaps-renderer.php</b> on line <b>126</b><br />
<?xml version="1.0" encoding="UTF-8"?>
<?xml-stylesheet type="text/xsl" href="https://ojorchester.de/wp-sitemap-index.xsl" ?>
<sitemapindex xmlns="http://www.sitemaps.org/schemas/sitemap/0.9"><sitemap><loc>https://ojorchester.de/wp-sitemap-posts-page-1.xml</loc></sitemap><sitemap><loc>https://ojorchester.de/wp-sitemap-users-1.xml</loc></sitemap></sitemapindex>