Require a captcha for visitor submissions and for login.

Without the form field, the check was skipped. A solved captcha lasts
30 minutes in the session.

publish/preview.inc.php

@@ -2,25 +2,6 @@
 $result = get_post_data(TRUE);
 extract($result[0], EXTR_OVERWRITE);
 
-if (isset($_POST['g-recaptcha-response'])) {
-  $captcha = $_POST['g-recaptcha-response'];
-  if (! $captcha) {
-    $validate['captcha'] = 'Invalid captcha. Please try again.';
-    include('./write.inc.php');
-    return;
-  }
-  $captcha_resp = file_get_contents("https://www.google.com/recaptcha/api/siteverify?secret=".urlencode(config('RECAPTCHA_SECRET'))."&response=".
-      $captcha."&remoteip=".$_SERVER['REMOTE_ADDR']);
-  var_dump($captcha_resp);
-  // PHP 8 treats the bare word "success" as an undefined constant, so decode the JSON reply
-  $captcha_json = json_decode((string)$captcha_resp);
-  if (empty($captcha_json->success)) {
-    $validate['captcha'] = 'The words you typed in the captcha were not correct. Please try again.';
-    include('./write.inc.php');
-    return;
-  }
-}
-
 echo '<p>Please review your submission. Once you\'ve finished, please click "Submit" at the bottom of the page, or click "Preview" to check it again.</p>';
 
 // Keep a new image outside the web root until the story is saved;