diff --git a/CRM/Twingle/Form/Profile.php b/CRM/Twingle/Form/Profile.php
index 2159d3b..086dc2b 100644
--- a/CRM/Twingle/Form/Profile.php
+++ b/CRM/Twingle/Form/Profile.php
@@ -607,7 +607,8 @@ class CRM_Twingle_Form_Profile extends CRM_Core_Form {
         if (!isset($profile_data[$key]) && $required) {
           CRM_Core_Session::setStatus(
             E::ts(
-              'The required configuration option "%1" has no value. Saving the profile might set this option to a possibly unwanted default value.',
+              'The required configuration option "%1" has no value.'
+              . ' Saving the profile might set this option to a possibly unwanted default value.',
               [1 => $metadata['label'] ?? $key]
             ),
             E::ts('Error'),
diff --git a/CRM/Twingle/Submission.php b/CRM/Twingle/Submission.php
index 70540ca..258f153 100644
--- a/CRM/Twingle/Submission.php
+++ b/CRM/Twingle/Submission.php
@@ -73,7 +73,7 @@ class CRM_Twingle_Submission {
     // Get the payment instrument defined within the profile, or return an error
     // if none matches (i.e. an unknown payment method was submitted).
     $payment_instrument_id = $profile->getAttribute('pi_' . $params['payment_method'], '');
-    if ('' !== $payment_instrument_id) {
+    if ('' === $payment_instrument_id) {
       throw new CRM_Core_Exception(
         E::ts('Payment method could not be matched to existing payment instrument.'),
         'invalid_format'
diff --git a/CRM/Twingle/Tools.php b/CRM/Twingle/Tools.php
index 9725a96..e2abc92 100644
--- a/CRM/Twingle/Tools.php
+++ b/CRM/Twingle/Tools.php
@@ -116,7 +116,10 @@ class CRM_Twingle_Tools {
    *   Recurring contribution fields.
    * @throws Exception could be one of the measures
    */
-  public static function processRecurringContributionTermination(int $recurring_contribution_id, array $recurring_contribution) {
+  public static function processRecurringContributionTermination(
+    int $recurring_contribution_id,
+    array $recurring_contribution
+  ) {
     // check if we're suspended
     if (self::$protection_suspended) {
       return;
diff --git a/api/v3/TwingleDonation/Submit.php b/api/v3/TwingleDonation/Submit.php
index d307424..daceb36 100644
--- a/api/v3/TwingleDonation/Submit.php
+++ b/api/v3/TwingleDonation/Submit.php
@@ -532,7 +532,7 @@ function civicrm_api3_twingle_donation_Submit($params) {
       : 'false';
     if (
       (bool) $profile->getAttribute('newsletter_double_opt_in')
-      && isset($params['newsletter'])
+      && (bool) ($params['newsletter'] ?? FALSE)
       && is_array($groups = $profile->getAttribute('newsletter_groups'))
     ) {
       $group_memberships = array_column(
@@ -572,7 +572,7 @@ function civicrm_api3_twingle_donation_Submit($params) {
       // If requested, add contact to newsletter groups defined in the profile.
     }
     elseif (
-      isset($params['newsletter'])
+      (bool) ($params['newsletter'] ?? FALSE)
       && is_array($groups = $profile->getAttribute('newsletter_groups'))
     ) {
       foreach ($groups as $group_id) {
@@ -591,7 +591,7 @@ function civicrm_api3_twingle_donation_Submit($params) {
 
     // If requested, add contact to postinfo groups defined in the profile.
     if (
-      isset($params['postinfo'])
+      (bool) ($params['postinfo'] ?? FALSE)
       && is_array($groups = $profile->getAttribute('postinfo_groups'))
     ) {
       foreach ($groups as $group_id) {
@@ -608,7 +608,7 @@ function civicrm_api3_twingle_donation_Submit($params) {
     // profile. If an organisation is provided, add it to the groups instead.
     // (see issue #83)
     if (
-      isset($params['donation_receipt'])
+      (bool) ($params['donation_receipt'] ?? FALSE)
       && is_array($groups = $profile->getAttribute('donation_receipt_groups'))
     ) {
       foreach ($groups as $group_id) {
@@ -666,7 +666,7 @@ function civicrm_api3_twingle_donation_Submit($params) {
       }
 
       $creditor_id = $profile->getAttribute('sepa_creditor_id');
-      if (!is_int($creditor_id)) {
+      if (!isset($creditor_id) || '' === $creditor_id) {
         throw new BaseException(
           E::ts('SEPA creditor is not configured for profile "%1".', [1 => $profile->getName()])
         );