diff --git a/lib/Fhp/BaseAction.php b/lib/Fhp/BaseAction.php
index d36dec6a..76ab7fc3 100644
--- a/lib/Fhp/BaseAction.php
+++ b/lib/Fhp/BaseAction.php
@@ -37,29 +37,24 @@
 abstract class BaseAction implements \Serializable
 {
     /** @var int[] Stores segment numbers that were assigned to the segments returned from {@link createRequest()}. */
-    protected $requestSegmentNumbers;
+    protected ?array $requestSegmentNumbers = null;
 
     /**
-     * @var string|null Contains the name of the segment, that might need a tan, used by FinTs::execute to signal
+     * Contains the name of the segment, that might need a tan, used by FinTs::execute to signal
      * to the bank that supplying a tan is supported.
      */
-    protected $needTanForSegment = null;
+    protected ?string $needTanForSegment = null;
 
-    /**
-     * If set, the last response from the server regarding this action asked for a TAN from the user.
-     * @var TanRequest|null
-     */
-    protected $tanRequest;
+    /** If set, the last response from the server regarding this action asked for a TAN from the user. */
+    protected ?TanRequest $tanRequest = null;
 
-    /** @var bool */
-    protected $isDone = false;
+    protected bool $isDone = false;
 
     /**
      * Will be populated with the message the bank sent along with the success indication, can be used to show to
      * the user.
-     * @var string
      */
-    public $successMessage;
+    public ?string $successMessage = null;
 
     /**
      * @deprecated Beginning from PHP7.4 __unserialize is used for new generated strings, then this method is only used for previously generated strings - remove after May 2023
@@ -231,7 +226,7 @@ public function processResponse(Message $response)
     /** @return int[] */
     public function getRequestSegmentNumbers(): array
     {
-        return $this->requestSegmentNumbers;
+        return $this->requestSegmentNumbers ?? [];
     }
 
     /**
diff --git a/lib/Fhp/Connection.php b/lib/Fhp/Connection.php
index 5b2981da..c461473d 100644
--- a/lib/Fhp/Connection.php
+++ b/lib/Fhp/Connection.php
@@ -7,25 +7,10 @@
  */
 class Connection
 {
-    /**
-     * @var string
-     */
-    protected $url;
-
-    /**
-     * @var resource
-     */
-    protected $curlHandle;
-
-    /**
-     * @var int
-     */
-    protected $timeoutConnect = 15;
-
-    /**
-     * @var int
-     */
-    protected $timeoutResponse = 30;
+    protected string $url;
+    protected ?\CurlHandle $curlHandle = null;
+    protected int $timeoutConnect = 15;
+    protected int $timeoutResponse = 30;
 
     public function __construct(string $url, int $timeoutConnect = 15, int $timeoutResponse = 30)
     {
@@ -34,9 +19,12 @@ public function __construct(string $url, int $timeoutConnect = 15, int $timeoutR
         $this->timeoutResponse = $timeoutResponse;
     }
 
-    private function connect()
+    /**
+     * @throws CurlException When initializing cURL fails.
+     */
+    private function connect(): void
     {
-        $this->curlHandle = curl_init();
+        $this->curlHandle = curl_init() ?: throw new CurlException('Failed initializing cURL.');
 
         curl_setopt($this->curlHandle, CURLOPT_SSL_VERIFYPEER, true);
         curl_setopt($this->curlHandle, CURLOPT_SSL_VERIFYHOST, 2);
@@ -52,7 +40,7 @@ private function connect()
         curl_setopt($this->curlHandle, CURLOPT_HTTPHEADER, ['cache-control: no-cache', 'Content-Type: text/plain']);
     }
 
-    public function disconnect()
+    public function disconnect(): void
     {
         if ($this->curlHandle !== null) {
             curl_close($this->curlHandle);
@@ -76,7 +64,7 @@ public function send(string $message): string
 
         if (false === $response) {
             throw new CurlException(
-                'Failed connection to ' . $this->url . ': ' . curl_error($this->curlHandle),
+                'Failed sending to ' . $this->url . ': ' . curl_error($this->curlHandle),
                 null,
                 curl_errno($this->curlHandle),
                 curl_getinfo($this->curlHandle),
diff --git a/lib/Fhp/Model/StatementOfAccount/Statement.php b/lib/Fhp/Model/StatementOfAccount/Statement.php
index 32237a50..b45e39f5 100644
--- a/lib/Fhp/Model/StatementOfAccount/Statement.php
+++ b/lib/Fhp/Model/StatementOfAccount/Statement.php
@@ -7,30 +7,12 @@ class Statement
     public const CD_CREDIT = 'credit';
     public const CD_DEBIT = 'debit';
 
-    /**
-     * @var array of Transaction
-     */
-    protected $transactions = [];
-
-    /**
-     * @var float
-     */
-    protected $startBalance = 0.0;
-
-    /**
-     * @var float|null
-     */
-    protected $endBalance = null;
-
-    /**
-     * @var string|null
-     */
-    protected $creditDebit = null;
-
-    /**
-     * @var \DateTime|null
-     */
-    protected $date;
+    /** @var Transaction[] */
+    protected array $transactions = [];
+    protected float $startBalance = 0.0;
+    protected ?float $endBalance = null;
+    protected ?string $creditDebit = null;
+    protected ?\DateTime $date = null;
 
     /**
      * Get transactions
diff --git a/lib/Fhp/Model/StatementOfAccount/StatementOfAccount.php b/lib/Fhp/Model/StatementOfAccount/StatementOfAccount.php
index 2cf2e603..1b5f9bfd 100644
--- a/lib/Fhp/Model/StatementOfAccount/StatementOfAccount.php
+++ b/lib/Fhp/Model/StatementOfAccount/StatementOfAccount.php
@@ -6,10 +6,8 @@
 
 class StatementOfAccount
 {
-    /**
-     * @var Statement[]
-     */
-    protected $statements = [];
+    /** @var Statement[] */
+    protected array $statements = [];
 
     /**
      * Get statements
diff --git a/lib/Fhp/Model/StatementOfAccount/Transaction.php b/lib/Fhp/Model/StatementOfAccount/Transaction.php
index 1483a30d..af3151fb 100644
--- a/lib/Fhp/Model/StatementOfAccount/Transaction.php
+++ b/lib/Fhp/Model/StatementOfAccount/Transaction.php
@@ -8,86 +8,28 @@ class Transaction
     public const CD_CREDIT = 'credit';
     public const CD_DEBIT = 'debit';
 
-    /**
-     * @var \DateTime|null
-     */
-    protected $bookingDate;
-
-    /**
-     * @var \DateTime|null
-     */
-    protected $valutaDate;
-
-    /**
-     * @var float
-     */
-    protected $amount;
-
-    /**
-     * @var string
-     */
-    protected $creditDebit;
-
-    /**
-     * @var bool
-     */
-    protected $isStorno;
-
-    /**
-     * @var string
-     */
-    protected $bookingCode;
-
-    /**
-     * @var string
-     */
-    protected $bookingText;
-
-    /**
-     * @var string
-     */
-    protected $description1;
-
-    /**
-     * @var string
-     */
-    protected $description2;
+    protected ?\DateTime $bookingDate = null;
+    protected ?\DateTime $valutaDate = null;
+    protected float $amount;
+    protected string $creditDebit;
+    protected bool $isStorno;
+    protected string $bookingCode;
+    protected string $bookingText;
+    protected string $description1;
+    protected string $description2;
 
     /**
      * Array keys are identifiers like "SVWZ" for the main description.
      * @var string[]
      */
-    protected $structuredDescription;
+    protected array $structuredDescription;
 
-    /**
-     * @var string
-     */
-    protected $bankCode;
-
-    /**
-     * @var string
-     */
-    protected $accountNumber;
-
-    /**
-     * @var string
-     */
-    protected $name;
-
-    /**
-     * @var bool
-     */
-    protected $booked;
-
-    /**
-     * @var int
-     */
-    protected $pn;
-
-    /**
-     * @var int
-     */
-    protected $textKeyAddition;
+    protected string $bankCode;
+    protected string $accountNumber;
+    protected string $name;
+    protected bool $booked;
+    protected int $pn;
+    protected int $textKeyAddition;
 
     /**
      * Get booking date.
@@ -121,10 +63,9 @@ public function getValutaDate(): ?\DateTime
      *
      * @return $this
      */
-    public function setBookingDate(?\DateTime $date = null)
+    public function setBookingDate(?\DateTime $date = null): static
     {
         $this->bookingDate = $date;
-
         return $this;
     }
 
@@ -133,10 +74,9 @@ public function setBookingDate(?\DateTime $date = null)
      *
      * @return $this
      */
-    public function setValutaDate(?\DateTime $date = null)
+    public function setValutaDate(?\DateTime $date = null): static
     {
         $this->valutaDate = $date;
-
         return $this;
     }
 
@@ -153,10 +93,9 @@ public function getAmount(): float
      *
      * @return $this
      */
-    public function setBooked(bool $booked)
+    public function setBooked(bool $booked): static
     {
         $this->booked = $booked;
-
         return $this;
     }
 
@@ -165,10 +104,9 @@ public function setBooked(bool $booked)
      *
      * @return $this
      */
-    public function setAmount(float $amount)
+    public function setAmount(float $amount): static
     {
-        $this->amount = (float) $amount;
-
+        $this->amount = $amount;
         return $this;
     }
 
@@ -185,10 +123,9 @@ public function getCreditDebit(): string
      *
      * @return $this
      */
-    public function setCreditDebit(string $creditDebit)
+    public function setCreditDebit(string $creditDebit): static
     {
         $this->creditDebit = $creditDebit;
-
         return $this;
     }
 
@@ -205,10 +142,9 @@ public function isStorno(): bool
      *
      * @return $this
      */
-    public function setIsStorno(bool $isStorno)
+    public function setIsStorno(bool $isStorno): static
     {
         $this->isStorno = $isStorno;
-
         return $this;
     }
 
@@ -225,10 +161,9 @@ public function getBookingCode(): string
      *
      * @return $this
      */
-    public function setBookingCode(string $bookingCode)
+    public function setBookingCode(string $bookingCode): static
     {
-        $this->bookingCode = (string) $bookingCode;
-
+        $this->bookingCode = $bookingCode;
         return $this;
     }
 
@@ -245,10 +180,9 @@ public function getBookingText(): string
      *
      * @return $this
      */
-    public function setBookingText(string $bookingText)
+    public function setBookingText(string $bookingText): static
     {
-        $this->bookingText = (string) $bookingText;
-
+        $this->bookingText = $bookingText;
         return $this;
     }
 
@@ -265,10 +199,9 @@ public function getDescription1(): string
      *
      * @return $this
      */
-    public function setDescription1(string $description1)
+    public function setDescription1(string $description1): static
     {
-        $this->description1 = (string) $description1;
-
+        $this->description1 = $description1;
         return $this;
     }
 
@@ -285,10 +218,9 @@ public function getDescription2(): string
      *
      * @return $this
      */
-    public function setDescription2(string $description2)
+    public function setDescription2(string $description2): static
     {
-        $this->description2 = (string) $description2;
-
+        $this->description2 = $description2;
         return $this;
     }
 
@@ -306,10 +238,9 @@ public function getStructuredDescription(): array
      * Set structuredDescription
      *
      * @param string[] $structuredDescription
-     *
      * @return $this
      */
-    public function setStructuredDescription(array $structuredDescription)
+    public function setStructuredDescription(array $structuredDescription): static
     {
         $this->structuredDescription = $structuredDescription;
 
@@ -353,10 +284,9 @@ public function getBankCode(): string
      *
      * @return $this
      */
-    public function setBankCode(string $bankCode)
+    public function setBankCode(string $bankCode): static
     {
-        $this->bankCode = (string) $bankCode;
-
+        $this->bankCode = $bankCode;
         return $this;
     }
 
@@ -373,10 +303,9 @@ public function getAccountNumber(): string
      *
      * @return $this
      */
-    public function setAccountNumber(string $accountNumber)
+    public function setAccountNumber(string $accountNumber): static
     {
-        $this->accountNumber = (string) $accountNumber;
-
+        $this->accountNumber = $accountNumber;
         return $this;
     }
 
@@ -401,10 +330,9 @@ public function getBooked(): bool
      *
      * @return $this
      */
-    public function setName(string $name)
+    public function setName(string $name): static
     {
-        $this->name = (string) $name;
-
+        $this->name = $name;
         return $this;
     }
 
@@ -422,7 +350,7 @@ public function getPN(): int
      * @param int|mixed $nr Will be parsed to an int.
      * @return $this
      */
-    public function setPN($nr)
+    public function setPN($nr): static
     {
         $this->pn = intval($nr);
         return $this;
@@ -442,7 +370,7 @@ public function getTextKeyAddition(): int
      * @param int|mixed $textKeyAddition Will be parsed to an int.
      * @return $this
      */
-    public function setTextKeyAddition($textKeyAddition)
+    public function setTextKeyAddition($textKeyAddition): static
     {
         $this->textKeyAddition = intval($textKeyAddition);
         return $this;
diff --git a/lib/Fhp/PaginateableAction.php b/lib/Fhp/PaginateableAction.php
index b01d4807..08a49ace 100644
--- a/lib/Fhp/PaginateableAction.php
+++ b/lib/Fhp/PaginateableAction.php
@@ -19,18 +19,17 @@
 abstract class PaginateableAction extends BaseAction
 {
     /**
-     * @var BaseSegment[] Stores the request created by BaseAction::getNextRequest to be reused in case the bank wants
+     * Stores the request created by BaseAction::getNextRequest to be reused in case the bank wants
      * to split the result over multiple pages e.g. request/response pairs. This avoids the need for {@link BPD} to be
      * available for paginated requests.
      */
-    protected $requestSegments;
+    protected ?array $requestSegments = null;
 
     /**
      * If set, the last response from the server regarding this action indicated that there are more results to be
      * fetched using this pagination token. This is called "Aufsetzpunkt" in the specification.
-     * @var string|null
      */
-    protected $paginationToken;
+    protected ?string $paginationToken = null;
 
     /**
      * @deprecated Beginning from PHP7.4 __unserialize is used for new generated strings, then this method is only used for previously generated strings - remove after May 2023