diff --git a/.github/workflows/build.yaml b/.github/workflows/build.yaml
index 127b445..df7eea1 100644
--- a/.github/workflows/build.yaml
+++ b/.github/workflows/build.yaml
@@ -6,11 +6,11 @@ on:
 
 jobs:
     phpstan:
-        runs-on: ubuntu-22.04
+        runs-on: ubuntu-24.04
         name: PHPStan
         steps:
             - name: Checkout
-              uses: actions/checkout@v3
+              uses: actions/checkout@v4
             - name: PHPStan
               uses: docker://oskarstark/phpstan-ga
               env:
@@ -18,30 +18,22 @@ jobs:
               with:
                   args: analyse
     cs-fixer:
-        runs-on: ubuntu-22.04
+        runs-on: ubuntu-24.04
         name: PHP-CS-Fixer
         steps:
             - name: Checkout
-              uses: actions/checkout@v3
+              uses: actions/checkout@v4
             - name: Fix CS
               uses: docker://oskarstark/php-cs-fixer-ga
     tests:
-        runs-on: ubuntu-20.04
+        runs-on: ubuntu-24.04
         strategy:
             max-parallel: 1
             matrix:
                 include:
                     - description: 'lowest'
-                      php: '7.1'
+                      php: '8.1'
                       composer_option: '--prefer-lowest'
-                    - description: '7.2'
-                      php: '7.2'
-                    - description: '7.3'
-                      php: '7.3'
-                    - description: '7.4'
-                      php: '7.4'
-                    - description: '8.0'
-                      php: '8.0'
                     - description: '8.1'
                       php: '8.1'
                     - description: '8.2'
@@ -51,10 +43,10 @@ jobs:
         name: PHP ${{ matrix.php }} tests
         steps:
             - name: Checkout
-              uses: actions/checkout@v3
+              uses: actions/checkout@v4
             - name: Cache
-              uses: actions/cache@v3
-              with: 
+              uses: actions/cache@v4
+              with:
                   path: ~/.composer/cache/files
                   key: ${{ matrix.php }}-${{ matrix.composer_option }} 
             - name: Setup PHP
diff --git a/.php-cs-fixer.php b/.php-cs-fixer.php
index 44d3103..e4c5e4c 100644
--- a/.php-cs-fixer.php
+++ b/.php-cs-fixer.php
@@ -10,8 +10,9 @@
     ->setRules([
         '@Symfony' => true,
         '@Symfony:risky' => true,
-        '@PHP71Migration:risky' => true,
-        '@PHPUnit75Migration:risky' => true,
+        '@PHP80Migration:risky' => true,
+        '@PHP81Migration' => true,
+        '@PHPUnit100Migration:risky' => true,
         'declare_strict_types' => false,
         'native_function_invocation' => ['include' => ['@all']],
         'final_class' => true,
diff --git a/README.md b/README.md
index d0b609b..530cb2c 100644
--- a/README.md
+++ b/README.md
@@ -40,7 +40,7 @@ $id = Shortid::generate();
 
 For more control, you can customize the alphabet and length using the Factory class.
 
-Default alphabet uses all letters (lowercase and uppercase), all numbers, underscore, and hypen.
+The default alphabet uses all letters (lowercase and uppercase), all numbers, underscore, and hyphen.
 
 ``` php
 use PUGX\Shortid\Factory;
@@ -52,14 +52,14 @@ $factory = new Factory();
 // alphabet string must be 64 characters long
 $factory->setAlphabet('é123456789àbcdefghìjklmnòpqrstùvwxyzABCDEFGHIJKLMNOPQRSTUVWX.!@|');
 // length must be between 2 and 20 (default is 7)
-// of course, a lower length is increasing clashing probability
+// of course, a lower length increases the clashing probability
 $factory->setLength(9);
 Shortid::setFactory($factory);
 
 $id = Shortid::generate();
 ```
 
-As alternative, you can customize single generations:
+As an alternative, you can customize single generations:
 
 ``` php
 use PUGX\Shortid\Shortid;
@@ -104,7 +104,7 @@ $anotherFixedId = new Shortid('fooBarZ');
 
 ## Doctrine
 
-If you want to use ShortId with Doctrine ORM, take a look to [ShortId Doctrine type][2].
+If you want to use ShortId with Doctrine ORM, take a look at [ShortId Doctrine type][2].
 
 
 ## Doctrine and Symfony
@@ -121,7 +121,7 @@ native extension is not available.
 If, instead, your environment is offering that extension, you can avoid installing
 that polyfill by configuring a [replace][5] entry in your `composer.json`.
 
-The same applies to the [randomLib][6] library: if you are using PHP 8.3 or higher, 
+The same applies to the [randomLib][6] library: if you are using PHP 8.3 or higher,
 you can replace it, since this library uses the native `Random` class instead.
 
 ## Contributing
diff --git a/composer.json b/composer.json
index 53d408e..4328aa4 100644
--- a/composer.json
+++ b/composer.json
@@ -20,21 +20,20 @@
         }
     ],
     "require": {
-        "php": "^7.1 || ^8.0",
-        "ext-json": "*",
+        "php": "^8.1",
         "paragonie/random-lib": "^2.0",
         "symfony/polyfill-mbstring": "^1.19"
     },
     "require-dev": {
         "dg/bypass-finals": "^1.3",
-        "phpunit/phpunit": "^7.5 || ^8.5 || ^9.5"
+        "phpunit/phpunit": "^9.6"
     },
     "config": {
         "bin-dir": "bin"
     },
     "extra": {
         "branch-alias": {
-            "dev-master": "1.0-dev"
+            "dev-master": "1.x-dev"
         }
     },
     "autoload": {
diff --git a/src/Factory.php b/src/Factory.php
index fef6151..cf6df50 100644
--- a/src/Factory.php
+++ b/src/Factory.php
@@ -8,33 +8,18 @@
 
 final class Factory
 {
-    /**
-     * @var int
-     */
-    private $length = 7;
-
-    /**
-     * @var string
-     */
-    private $alphabet = '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ_-';
-
-    /**
-     * @var bool
-     */
-    private $readable = false;
-
-    /**
-     * @var RandomLibFactory
-     */
-    private static $factory;
+    private int $length = 7;
+    private string $alphabet = '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ_-';
+    private bool $readable = false;
+    private static ?RandomLibFactory $factory = null;
 
     /**
      * @throws InvalidShortidException
      */
-    public function generate(int $length = null, string $alphabet = null, bool $readable = null): Shortid
+    public function generate(?int $length = null, ?string $alphabet = null, ?bool $readable = null): Shortid
     {
-        $length = $length ?? $this->length;
-        $readable = $readable ?? $this->readable;
+        $length ??= $this->length;
+        $readable ??= $this->readable;
         if (null === $alphabet && $readable) {
             $alphabet = \str_replace(\str_split(Generator::AMBIGUOUS_CHARS), '', $this->alphabet);
             $alphabet .= \str_repeat('_', \strlen(Generator::AMBIGUOUS_CHARS) / 2);
@@ -80,7 +65,7 @@ public static function getFactory(): RandomLibFactory
         return self::$factory;
     }
 
-    public function checkLength(int $length = null, bool $strict = false): void
+    public function checkLength(?int $length = null, bool $strict = false): void
     {
         if (null === $length && !$strict) {
             return;
diff --git a/src/Shortid.php b/src/Shortid.php
index 10d1415..33c7c6d 100644
--- a/src/Shortid.php
+++ b/src/Shortid.php
@@ -2,28 +2,18 @@
 
 namespace PUGX\Shortid;
 
-final class Shortid implements \JsonSerializable, \Serializable
+final class Shortid implements \JsonSerializable, \Serializable, \Stringable
 {
-    /**
-     * @var string
-     */
-    private $id;
-
-    /**
-     * @var Factory|null
-     */
-    private static $factory;
+    private static ?Factory $factory = null;
 
     /**
      * @throws InvalidShortidException
      */
-    public function __construct(string $id, int $length = null, string $alphabet = null)
+    public function __construct(private string $id, ?int $length = null, ?string $alphabet = null)
     {
         if (!self::isValid($id, $length, $alphabet)) {
             throw new InvalidShortidException(\sprintf('Invalid shortid %s (length %d alphabet %s', $id, $length, $alphabet));
         }
-
-        $this->id = $id;
     }
 
     public function __toString(): string
@@ -34,7 +24,7 @@ public function __toString(): string
     /**
      * @throws InvalidShortidException
      */
-    public static function generate(int $length = null, string $alphabet = null, bool $readable = false): self
+    public static function generate(?int $length = null, ?string $alphabet = null, bool $readable = false): self
     {
         if (null === $length) {
             self::getFactory()->checkLength($length);
@@ -53,14 +43,14 @@ public static function getFactory(): Factory
         return self::$factory;
     }
 
-    public static function setFactory(Factory $factory = null): void
+    public static function setFactory(?Factory $factory = null): void
     {
         self::$factory = $factory;
     }
 
-    public static function isValid(string $value, int $length = null, string $alphabet = null): bool
+    public static function isValid(string $value, ?int $length = null, ?string $alphabet = null): bool
     {
-        $length = $length ?? self::getFactory()->getLength();
+        $length ??= self::getFactory()->getLength();
         $alphabet = \preg_quote($alphabet ?: self::getFactory()->getAlphabet(), '/');
         $matches = [];
         $ok = \preg_match('/^(['.$alphabet.']{'.$length.'})$/', $value, $matches);
@@ -78,12 +68,9 @@ public function serialize(): string
         return $this->id;
     }
 
-    /**
-     * @param string $serialized
-     */
-    public function unserialize($serialized): void
+    public function unserialize(string $data): void
     {
-        $this->id = $serialized;
+        $this->id = $data;
     }
 
     /**
diff --git a/tests/FactoryTest.php b/tests/FactoryTest.php
index 5e584ed..aa57aa9 100644
--- a/tests/FactoryTest.php
+++ b/tests/FactoryTest.php
@@ -8,10 +8,7 @@
 
 final class FactoryTest extends TestCase
 {
-    /**
-     * @var Factory
-     */
-    private $factory;
+    private Factory $factory;
 
     protected function setUp(): void
     {
@@ -25,14 +22,14 @@ public function testGenerate(): void
         if (\method_exists($this, 'assertMatchesRegularExpression')) {
             self::assertMatchesRegularExpression('/^[a-z0-9\_\-]{7}$/i', $generated->__toString());
         } else {
-            self::assertRegExp('/^[a-z0-9\_\-]{7}$/i', $generated->__toString());
+            self::assertMatchesRegularExpression('/^[a-z0-9\_\-]{7}$/i', $generated->__toString());
         }
     }
 
     /**
      * @return string[][]
      */
-    public function alphabetsProvider(): array
+    public static function alphabetsProvider(): array
     {
         $alphabets = [];
         $chars = [];
@@ -77,7 +74,7 @@ public function testSetWrongAlphabet(string $alphabet): void
     /**
      * @return array{test: array{'test'}, rand: array{string}}
      */
-    public function wrongAlphabetsProvider(): array
+    public static function wrongAlphabetsProvider(): array
     {
         return [
             'test' => ['test'],
diff --git a/tests/ShortidTest.php b/tests/ShortidTest.php
index 35fd53f..66f06c4 100644
--- a/tests/ShortidTest.php
+++ b/tests/ShortidTest.php
@@ -21,7 +21,7 @@ public function testGenerate(): void
         if (\method_exists($this, 'assertMatchesRegularExpression')) {
             self::assertMatchesRegularExpression('/^[a-z0-9\_\-]{7}$/i', $generated->__toString());
         } else {
-            self::assertRegExp('/^[a-z0-9\_\-]{7}$/i', $generated->__toString());
+            self::assertMatchesRegularExpression('/^[a-z0-9\_\-]{7}$/i', $generated->__toString());
         }
     }
 
@@ -32,7 +32,7 @@ public function testGenerateWithReadable(): void
         if (\method_exists($this, 'assertMatchesRegularExpression')) {
             self::assertMatchesRegularExpression('/^[a-z0-9\_\-]{7}$/i', $generated->__toString());
         } else {
-            self::assertRegExp('/^[a-z0-9\_\-]{7}$/i', $generated->__toString());
+            self::assertMatchesRegularExpression('/^[a-z0-9\_\-]{7}$/i', $generated->__toString());
         }
     }
 
@@ -43,7 +43,7 @@ public function testGenerateWithLength(): void
         if (\method_exists($this, 'assertMatchesRegularExpression')) {
             self::assertMatchesRegularExpression('/^[a-z0-9\_\-]{8}$/i', $generated->__toString());
         } else {
-            self::assertRegExp('/^[a-z0-9\_\-]{8}$/i', $generated->__toString());
+            self::assertMatchesRegularExpression('/^[a-z0-9\_\-]{8}$/i', $generated->__toString());
         }
     }