diff --git a/apps/dav/lib/CalDAV/CalDavBackend.php b/apps/dav/lib/CalDAV/CalDavBackend.php
index a6c00a59174ce..1424ee4f9be2a 100644
--- a/apps/dav/lib/CalDAV/CalDavBackend.php
+++ b/apps/dav/lib/CalDAV/CalDavBackend.php
@@ -2347,7 +2347,7 @@ public function getCalendarObjectById(string $principalUri, int $id): ?array {
 	 * @param int $syncLevel
 	 * @param int|null $limit
 	 * @param int $calendarType
-	 * @return array
+	 * @return ?array
 	 */
 	public function getChangesForCalendar($calendarId, $syncToken, $syncLevel, $limit = null, $calendarType = self::CALENDAR_TYPE_CALENDAR) {
 		$table = $calendarType === self::CALENDAR_TYPE_CALENDAR ? 'calendars': 'calendarsubscriptions';
diff --git a/lib/private/AppFramework/Utility/SimpleContainer.php b/lib/private/AppFramework/Utility/SimpleContainer.php
index 83aed4381b342..f9ab02a120700 100644
--- a/lib/private/AppFramework/Utility/SimpleContainer.php
+++ b/lib/private/AppFramework/Utility/SimpleContainer.php
@@ -60,7 +60,7 @@ public function __construct() {
 	 * @psalm-param S $id
 	 * @psalm-return (S is class-string<T> ? T : mixed)
 	 */
-	public function get(string $id) {
+	public function get(string $id): object {
 		return $this->query($id);
 	}
 
diff --git a/lib/private/Authentication/TwoFactorAuth/Db/ProviderUserAssignmentDao.php b/lib/private/Authentication/TwoFactorAuth/Db/ProviderUserAssignmentDao.php
index db5da97f27588..c1b1d3d74225f 100644
--- a/lib/private/Authentication/TwoFactorAuth/Db/ProviderUserAssignmentDao.php
+++ b/lib/private/Authentication/TwoFactorAuth/Db/ProviderUserAssignmentDao.php
@@ -91,8 +91,6 @@ public function persist(string $providerId, string $uid, int $enabled): void {
 	/**
 	 * Delete all provider states of a user and return the provider IDs
 	 *
-	 * @param string $uid
-	 *
 	 * @return list<array{provider_id: string, uid: string, enabled: bool}>
 	 */
 	public function deleteByUser(string $uid): array {
@@ -100,7 +98,7 @@ public function deleteByUser(string $uid): array {
 		$selectQuery = $qb1->select('*')
 			->from(self::TABLE_NAME)
 			->where($qb1->expr()->eq('uid', $qb1->createNamedParameter($uid)));
-		$selectResult = $selectQuery->execute();
+		$selectResult = $selectQuery->executeQuery();
 		$rows = $selectResult->fetchAll();
 		$selectResult->closeCursor();
 
@@ -108,15 +106,15 @@ public function deleteByUser(string $uid): array {
 		$deleteQuery = $qb2
 			->delete(self::TABLE_NAME)
 			->where($qb2->expr()->eq('uid', $qb2->createNamedParameter($uid)));
-		$deleteQuery->execute();
+		$deleteQuery->executeStatement();
 
-		return array_map(function (array $row) {
+		return array_values(array_map(function (array $row) {
 			return [
-				'provider_id' => $row['provider_id'],
-				'uid' => $row['uid'],
-				'enabled' => (int) $row['enabled'] === 1,
+				'provider_id' => (string)$row['provider_id'],
+				'uid' => (string)$row['uid'],
+				'enabled' => $row['enabled'] === 1,
 			];
-		}, $rows);
+		}, $rows));
 	}
 
 	public function deleteAll(string $providerId): void {
diff --git a/lib/private/DB/QueryBuilder/Literal.php b/lib/private/DB/QueryBuilder/Literal.php
index b4e8a36b86fca..321a836abc77a 100644
--- a/lib/private/DB/QueryBuilder/Literal.php
+++ b/lib/private/DB/QueryBuilder/Literal.php
@@ -32,10 +32,7 @@ public function __construct($literal) {
 		$this->literal = $literal;
 	}
 
-	/**
-	 * @return string
-	 */
-	public function __toString() {
+	public function __toString(): string {
 		return (string) $this->literal;
 	}
 }
diff --git a/lib/private/DB/QueryBuilder/Parameter.php b/lib/private/DB/QueryBuilder/Parameter.php
index b6cfa844e01ac..148580447bddf 100644
--- a/lib/private/DB/QueryBuilder/Parameter.php
+++ b/lib/private/DB/QueryBuilder/Parameter.php
@@ -31,10 +31,7 @@ public function __construct($name) {
 		$this->name = $name;
 	}
 
-	/**
-	 * @return string
-	 */
-	public function __toString() {
+	public function __toString(): string {
 		return (string) $this->name;
 	}
 }
diff --git a/lib/private/DB/QueryBuilder/QueryFunction.php b/lib/private/DB/QueryBuilder/QueryFunction.php
index 41798f233cde9..c0fd38150efdd 100644
--- a/lib/private/DB/QueryBuilder/QueryFunction.php
+++ b/lib/private/DB/QueryBuilder/QueryFunction.php
@@ -31,10 +31,7 @@ public function __construct($function) {
 		$this->function = $function;
 	}
 
-	/**
-	 * @return string
-	 */
-	public function __toString() {
+	public function __toString(): string {
 		return (string) $this->function;
 	}
 }
diff --git a/lib/private/DateTimeFormatter.php b/lib/private/DateTimeFormatter.php
index 0c5b6a55882f2..10c7703d9b608 100644
--- a/lib/private/DateTimeFormatter.php
+++ b/lib/private/DateTimeFormatter.php
@@ -138,12 +138,11 @@ public function formatDateRelativeDay($timestamp, $format = 'long', ?\DateTimeZo
 	 *
 	 * @param int|\DateTime	$timestamp	Either a Unix timestamp or DateTime object
 	 * @param int|\DateTime	$baseTimestamp	Timestamp to compare $timestamp against, defaults to current time
+	 * @param \OCP\IL10N	$l			The locale to use
 	 * @return string	Dates returned are:
 	 * 				<  1 month	=> Today, Yesterday, n days ago
 	 * 				< 13 month	=> last month, n months ago
 	 * 				>= 13 month	=> last year, n years ago
-	 * @param \OCP\IL10N	$l			The locale to use
-	 * @return string Formatted date span
 	 */
 	public function formatDateSpan($timestamp, $baseTimestamp = null, ?\OCP\IL10N $l = null) {
 		$l = $this->getLocale($l);
@@ -220,15 +219,14 @@ public function formatTime($timestamp, $format = 'medium', ?\DateTimeZone $timeZ
 	 *
 	 * @param int|\DateTime	$timestamp	Either a Unix timestamp or DateTime object
 	 * @param int|\DateTime	$baseTimestamp	Timestamp to compare $timestamp against, defaults to current time
-	 * @return string	Dates returned are:
+	 * @param \OCP\IL10N	$l			The locale to use
+	 * @return string Dates returned are:
 	 * 				< 60 sec	=> seconds ago
 	 * 				<  1 hour	=> n minutes ago
 	 * 				<  1 day	=> n hours ago
 	 * 				<  1 month	=> Yesterday, n days ago
 	 * 				< 13 month	=> last month, n months ago
 	 * 				>= 13 month	=> last year, n years ago
-	 * @param \OCP\IL10N	$l			The locale to use
-	 * @return string Formatted time span
 	 */
 	public function formatTimeSpan($timestamp, $baseTimestamp = null, ?\OCP\IL10N $l = null) {
 		$l = $this->getLocale($l);
diff --git a/lib/private/Diagnostics/Event.php b/lib/private/Diagnostics/Event.php
index 0c3aa6ae29ce4..554f54a6ffdc3 100644
--- a/lib/private/Diagnostics/Event.php
+++ b/lib/private/Diagnostics/Event.php
@@ -101,7 +101,7 @@ public function getDuration() {
 		return $this->end - $this->start;
 	}
 
-	public function __toString() {
+	public function __toString(): string {
 		return $this->getId() . ' ' . $this->getDescription() . ' ' . $this->getDuration();
 	}
 }
diff --git a/lib/private/legacy/OC_Image.php b/lib/private/legacy/OC_Image.php
index 48f1812038ba0..28d4af118f0d9 100644
--- a/lib/private/legacy/OC_Image.php
+++ b/lib/private/legacy/OC_Image.php
@@ -419,7 +419,7 @@ public function data(): ?string {
 	/**
 	 * @return string - base64 encoded, which is suitable for embedding in a VCard.
 	 */
-	public function __toString() {
+	public function __toString(): string {
 		return base64_encode($this->data());
 	}
 
diff --git a/lib/public/Files/LockNotAcquiredException.php b/lib/public/Files/LockNotAcquiredException.php
index 000c532063459..e010ef244e463 100644
--- a/lib/public/Files/LockNotAcquiredException.php
+++ b/lib/public/Files/LockNotAcquiredException.php
@@ -50,10 +50,9 @@ public function __construct($path, $lockType, $code = 0, ?\Exception $previous =
 	/**
 	 * custom string representation of object
 	 *
-	 * @return string
 	 * @since 7.0.0
 	 */
-	public function __toString() {
+	public function __toString(): string {
 		return __CLASS__ . ": [{$this->code}]: {$this->message}\n";
 	}
 }