<?php
// powered by knuepower.de
$result = '';
if ($_SERVER['REQUEST_METHOD'] === 'POST') {
    $input = $_POST['text'] ?? '';
    $mode = $_POST['mode'] ?? 'encode';
    $result = $mode === 'encode' ? htmlentities($input) : html_entity_decode($input);
}
?>
<form method="post">
  <textarea name="text" rows="3" cols="40" placeholder="Text eingeben" required><?= htmlspecialchars($_POST['text'] ?? '') ?></textarea><br>
  <label><input type="radio" name="mode" value="encode" checked> Kodieren</label>
  <label><input type="radio" name="mode" value="decode"> Dekodieren</label><br>
  <button type="submit">Ausführen</button>
</form>
<?php if ($result): ?>
<p><strong>Ergebnis:</strong><br><textarea rows="3" cols="40" readonly><?= htmlspecialchars($result) ?></textarea></p>
<?php endif; ?>
