diff --git a/src/Module/Admin/Themes/Embed.php b/src/Module/Admin/Themes/Embed.php
index 00a79db54d..64f686a1ab 100644
--- a/src/Module/Admin/Themes/Embed.php
+++ b/src/Module/Admin/Themes/Embed.php
@@ -49,7 +49,7 @@ class Embed extends BaseAdmin
 			require_once "view/theme/$theme/config.php";
 			if (function_exists('theme_admin_post')) {
 				self::checkFormSecurityTokenRedirectOnError('/admin/themes/' . $theme . '/embed?mode=minimal', 'admin_theme_settings');
-				theme_admin_post($this->appHelper);
+				theme_admin_post();
 			}
 		}
 
diff --git a/src/Module/Api/Mastodon/Markers.php b/src/Module/Api/Mastodon/Markers.php
index b5ed3e825a..11ae2e9324 100644
--- a/src/Module/Api/Mastodon/Markers.php
+++ b/src/Module/Api/Mastodon/Markers.php
@@ -31,7 +31,7 @@ class Markers extends BaseApi
 			}
 		}
 
-		if (empty($timeline) || empty($last_read_id) || empty($application['id'])) {
+		if ($timeline === '' || $last_read_id === '' || empty($application['id'])) {
 			$this->logAndJsonError(422, $this->errorFactory->UnprocessableEntity());
 		}
 
diff --git a/src/Module/Api/Twitter/Friendships/Show.php b/src/Module/Api/Twitter/Friendships/Show.php
index 1c2bea6cba..2099bf16a9 100644
--- a/src/Module/Api/Twitter/Friendships/Show.php
+++ b/src/Module/Api/Twitter/Friendships/Show.php
@@ -28,12 +28,12 @@ class Show extends ContactEndpoint
 		$target_cid = BaseApi::getContactIDForSearchterm($this->getRequestValue($request, 'target_screen_name', ''), '', $this->getRequestValue($request, 'target_id', 0), $uid);
 
 		$source = Contact::getById($source_cid);
-		if (empty($source)) {
+		if ($source === false) {
 			throw new NotFoundException('Source not found');
 		}
 
 		$target = Contact::getById($target_cid);
-		if (empty($source)) {
+		if ($target === false) {
 			throw new NotFoundException('Target not found');
 		}
 
diff --git a/src/Module/BaseNotifications.php b/src/Module/BaseNotifications.php
index f9f47d4a21..0445075995 100644
--- a/src/Module/BaseNotifications.php
+++ b/src/Module/BaseNotifications.php
@@ -131,7 +131,7 @@ abstract class BaseNotifications extends BaseModule
 
 		$notif_tpl = Renderer::getMarkupTemplate('notifications/notifications.tpl');
 		return Renderer::replaceMacros($notif_tpl, [
-			'$header'        => $header ?? $this->t('Notifications'),
+			'$header'        => $header ?: $this->t('Notifications'),
 			'$tabs'          => $tabs,
 			'$notifications' => $notifications,
 			'$noContent'     => $noContent,
diff --git a/src/Module/Calendar/Event/API.php b/src/Module/Calendar/Event/API.php
index 3223ecd42b..8a62efdc8a 100644
--- a/src/Module/Calendar/Event/API.php
+++ b/src/Module/Calendar/Event/API.php
@@ -140,9 +140,9 @@ class API extends BaseModule
 		$share     = intval($request['share'] ?? 0);
 		$isPreview = intval($request['preview'] ?? 0);
 
-		$start = DateTimeFormat::convert($strStartDateTime ?? DBA::NULL_DATETIME, 'UTC', $this->timezone);
+		$start = DateTimeFormat::convert($strStartDateTime, 'UTC', $this->timezone);
 		if (!$noFinish) {
-			$finish = DateTimeFormat::convert($strFinishDateTime ?? DBA::NULL_DATETIME, 'UTC', $this->timezone);
+			$finish = DateTimeFormat::convert($strFinishDateTime, 'UTC', $this->timezone);
 		} else {
 			$finish = DBA::NULL_DATETIME;
 		}
diff --git a/src/Module/Circle.php b/src/Module/Circle.php
index ae81d3f757..b638eec557 100644
--- a/src/Module/Circle.php
+++ b/src/Module/Circle.php
@@ -70,6 +70,8 @@ class Circle extends BaseModule
 				throw new \Exception(DI::l10n()->t('Permission denied.'), 403);
 			}
 
+			$message = '';
+
 			if (isset($this->parameters['command'])) {
 				$circle_id = $this->parameters['circle'];
 				$contact_id = $this->parameters['contact'];
@@ -169,7 +171,9 @@ class Circle extends BaseModule
 			]);
 		}
 
-		$nocircle = false;
+		$nocircle    = false;
+		$members     = [];
+		$preselected = [];
 
 		// @TODO: Replace with parameter from router
 		if ((DI::args()->getArgc() == 2) && (DI::args()->getArgv()[1] === 'none') ||
@@ -181,9 +185,6 @@ class Circle extends BaseModule
 				'name' => DI::l10n()->t('Contacts not in any circle'),
 			];
 
-			$members = [];
-			$preselected = [];
-
 			$context = $context + [
 				'$title' => $circle['name'],
 				'$gname' => ['circle_name', DI::l10n()->t('Circle Name: '), $circle['name'], ''],
diff --git a/view/theme/duepuntozero/config.php b/view/theme/duepuntozero/config.php
index 1c70b4414c..35629a9143 100644
--- a/view/theme/duepuntozero/config.php
+++ b/view/theme/duepuntozero/config.php
@@ -42,7 +42,7 @@ function theme_admin(AppHelper $appHelper)
 	return clean_form($appHelper, $colorset, $user);
 }
 
-function theme_admin_post(AppHelper $appHelper)
+function theme_admin_post()
 {
 	if (isset($_POST['duepuntozero-settings-submit'])) {
 		DI::config()->set('duepuntozero', 'colorset', $_POST['duepuntozero_colorset']);
diff --git a/view/theme/quattro/config.php b/view/theme/quattro/config.php
index 97f68c0579..4406b3d9ea 100644
--- a/view/theme/quattro/config.php
+++ b/view/theme/quattro/config.php
@@ -46,7 +46,7 @@ function theme_admin(AppHelper $appHelper) {
 	return quattro_form($appHelper,$align, $color, $tfs, $pfs);
 }
 
-function theme_admin_post(AppHelper $appHelper) {
+function theme_admin_post() {
 	if (isset($_POST['quattro-settings-submit'])){
 		DI::config()->set('quattro', 'align', $_POST['quattro_align']);
 		DI::config()->set('quattro', 'color', $_POST['quattro_color']);
diff --git a/view/theme/vier/config.php b/view/theme/vier/config.php
index f30bf1be7e..f69e9521a7 100644
--- a/view/theme/vier/config.php
+++ b/view/theme/vier/config.php
@@ -91,7 +91,7 @@ function theme_admin(AppHelper $appHelper) {
 	return $o;
 }
 
-function theme_admin_post(AppHelper $appHelper) {
+function theme_admin_post() {
 	if (isset($_POST['vier-settings-submit'])){
 		DI::config()->set('vier', 'style', $_POST['vier_style']);
 		DI::config()->set('vier', 'show_pages', $_POST['vier_show_pages']);