app/Config/Encryption.php

 <?php
 
+declare(strict_types=1);
+
 namespace Config;
 
 use CodeIgniter\Config\BaseConfig;
@@ -7,8 +9,8 @@ use CodeIgniter\Config\BaseConfig;
 /**
  * Encryption configuration.
  *
- * These are the settings used for encryption, if you don't pass a parameter
- * array to the encrypter for creation/initialization.
+ * These are the settings used for encryption, if you don't pass a parameter array to the encrypter for
+ * creation/initialization.
  */
 class Encryption extends BaseConfig
 {
@@ -20,10 +22,8 @@ class Encryption extends BaseConfig
      * If you use the Encryption class you must set an encryption key (seed).
      * You need to ensure it is long enough for the cipher and mode you plan to use.
      * See the user guide for more info.
-     *
-     * @var string
      */
-    public $key = '';
+    public string $key = '';
 
     /**
      * --------------------------------------------------------------------------
@@ -35,10 +35,8 @@ class Encryption extends BaseConfig
      * Available drivers:
      * - OpenSSL
      * - Sodium
-     *
-     * @var string
      */
-    public $driver = 'OpenSSL';
+    public string $driver = 'OpenSSL';
 
     /**
      * --------------------------------------------------------------------------
@@ -49,10 +47,8 @@ class Encryption extends BaseConfig
      * before it is encrypted. This value should be greater than zero.
      *
      * See the user guide for more information on padding.
-     *
-     * @var integer
      */
-    public $blockSize = 16;
+    public int $blockSize = 16;
 
     /**
      * --------------------------------------------------------------------------
@@ -60,8 +56,39 @@ class Encryption extends BaseConfig
      * --------------------------------------------------------------------------
      *
      * HMAC digest to use, e.g. 'SHA512' or 'SHA256'. Default value is 'SHA512'.
+     */
+    public string $digest = 'SHA512';
+
+    /**
+     * Whether the cipher-text should be raw. If set to false, then it will be base64 encoded.
+     * This setting is only used by OpenSSLHandler.
+     *
+     * Set to false for CI3 Encryption compatibility.
+     */
+    public bool $rawData = true;
+
+    /**
+     * Encryption key info.
+     * This setting is only used by OpenSSLHandler.
+     *
+     * Set to 'encryption' for CI3 Encryption compatibility.
+     */
+    public string $encryptKeyInfo = '';
+
+    /**
+     * Authentication key info.
+     * This setting is only used by OpenSSLHandler.
+     *
+     * Set to 'authentication' for CI3 Encryption compatibility.
+     */
+    public string $authKeyInfo = '';
+
+    /**
+     * Cipher to use.
+     * This setting is only used by OpenSSLHandler.
      *
-     * @var string
+     * Set to 'AES-128-CBC' to decrypt encrypted data that encrypted
+     * by CI3 Encryption default configuration.
      */
-    public $digest = 'SHA512';
+    public string $cipher = 'AES-256-CTR';
 }

app/Config/Feature.php

+<?php
+
+declare(strict_types=1);
+
+namespace Config;
+
+use CodeIgniter\Config\BaseConfig;
+
+/**
+ * Enable/disable backward compatibility breaking features.
+ */
+class Feature extends BaseConfig
+{
+    /**
+     * Use improved new auto routing instead of the legacy version.
+     */
+    public bool $autoRoutesImproved = true;
+
+    /**
+     * Use filter execution order in 4.4 or before.
+     */
+    public bool $oldFilterOrder = false;
+
+    /**
+     * The behavior of `limit(0)` in Query Builder.
+     *
+     * If true, `limit(0)` returns all records. (the behavior of 4.4.x or before in version 4.x.)
+     * If false, `limit(0)` returns no records. (the behavior of 3.1.9 or later in version 3.x.)
+     */
+    public bool $limitZeroAsAll = true;
+
+    /**
+     * Use strict location negotiation.
+     *
+     * By default, the locale is selected based on a loose comparison of the language code (ISO 639-1)
+     * Enabling strict comparison will also consider the region code (ISO 3166-1 alpha-2).
+     */
+    public bool $strictLocaleNegotiation = false;
+}

app/Config/ForeignCharacters.php

 <?php
 
+declare(strict_types=1);
+
 namespace Config;
 
 use CodeIgniter\Config\ForeignCharacters as BaseForeignCharacters;
 
+/**
+ * @immutable
+ */
 class ForeignCharacters extends BaseForeignCharacters
 {
 }