diff --git a/.github/workflows/test.yaml b/.github/workflows/test.yaml
index bca7243..4ec3158 100644
--- a/.github/workflows/test.yaml
+++ b/.github/workflows/test.yaml
@@ -9,6 +9,8 @@ jobs:
         runs-on: ubuntu-22.04
 
         strategy:
+            fail-fast: false
+            experimental: [false]
             matrix:
                 php-version:
                     - 7.3
@@ -17,6 +19,9 @@ jobs:
                     - 8.1
                     - 8.2
                     - 8.3
+            include:
+              - php: 8.2
+                analysis: true
                     
 
         steps:
@@ -35,5 +40,9 @@ jobs:
               with:
                   composer-options: --prefer-dist
 
+            - name: Static analysis
+              if: matrix.analysis
+              run: vendor/bin/phpstan
+
             - name: Run Tests
               run: vendor/bin/phpunit
diff --git a/composer.json b/composer.json
index ab5bc1e..f92c309 100644
--- a/composer.json
+++ b/composer.json
@@ -2,7 +2,6 @@
     "name": "kohanaworld/hmmmath",
     "description": "Collection of math related PHP functions (PHP >=7.2 <=8.3",
     "license": "MIT",
-    "version": "0.9.0",
     "authors": [
         {
             "name": "Lars Strojny",
@@ -24,9 +23,11 @@
         }
     },
     "require": {
-        "php": "^7.3|^8.0"
+        "php": "^7.4|^8.0"
     },
     "require-dev": {
-        "phpunit/phpunit": "^9"
+        "phpunit/phpunit": "^9",
+        "phpstan/phpstan": "^1.11",
+        "squizlabs/php_codesniffer": "3.*"
     }
 }
diff --git a/phpstan.neon.dist b/phpstan.neon.dist
new file mode 100644
index 0000000..16c0677
--- /dev/null
+++ b/phpstan.neon.dist
@@ -0,0 +1,5 @@
+parameters:
+    level: 2
+    paths:
+        - src
+        - tests
\ No newline at end of file
diff --git a/src/hmmmath/Exception/BadMethodCallException.php b/src/hmmmath/Exception/BadMethodCallException.php
index f4d6ac8..95e1fda 100644
--- a/src/hmmmath/Exception/BadMethodCallException.php
+++ b/src/hmmmath/Exception/BadMethodCallException.php
@@ -3,7 +3,7 @@
 
 use InvalidArgumentException as BaseBadMethodCallException;
 
-class BadMethodCallException extends BaseBadMethodCallException
+final class BadMethodCallException extends BaseBadMethodCallException
 {
     public static function invalidMethod(string $className, string $methodName): self
     {
diff --git a/src/hmmmath/Exception/InvalidArgumentException.php b/src/hmmmath/Exception/InvalidArgumentException.php
index 1c644e8..ff38d66 100644
--- a/src/hmmmath/Exception/InvalidArgumentException.php
+++ b/src/hmmmath/Exception/InvalidArgumentException.php
@@ -3,7 +3,7 @@
 
 use InvalidArgumentException as BaseInvalidArgumentException;
 
-class InvalidArgumentException extends BaseInvalidArgumentException
+final class InvalidArgumentException extends BaseInvalidArgumentException
 {
     /**
      * @param mixed $actualValue
diff --git a/src/hmmmath/Fibonacci/FibonacciFactory.php b/src/hmmmath/Fibonacci/FibonacciFactory.php
index 753adea..d77c968 100644
--- a/src/hmmmath/Fibonacci/FibonacciFactory.php
+++ b/src/hmmmath/Fibonacci/FibonacciFactory.php
@@ -1,18 +1,24 @@
 <?php
 namespace hmmmath\Fibonacci;
 
+use ArrayIterator;
 use hmmmath\Exception\InvalidArgumentException;
 use Traversable;
 use LimitIterator;
 
 class FibonacciFactory
 {
-    /**
-     * Create fibonacci sequence
-     *
-     * The sequence is infinite but the factory method optionally takes a third argument to limit the sequence. A fourth
-     * parameter can be passed to specify an offset for the sequence.
-     */
+	/**
+	 * Create fibonacci sequence
+	 *
+	 * The sequence is infinite but the factory method optionally takes a third argument to limit the sequence. A fourth
+	 * parameter can be passed to specify an offset for the sequence.
+	 * @param int $start
+	 * @param int $increment
+	 * @param int $limit
+	 * @param int $offset
+	 * @return Traversable
+	 */
     public static function sequence(int $start = 0, int $increment = 1, int $limit = 0, int $offset = 0): Traversable
     {
         $sequence = new FibonacciSequence($start, $increment);
@@ -26,7 +32,7 @@ public static function sequence(int $start = 0, int $increment = 1, int $limit =
 
         return $sequence;
     }
-
+//@return ArrayIterator<int, FibonacciSequence>|LimitIterator<mixed, mixed,FibonacciSequence>
     /** Create fibonacci number */
     public static function number(int $start = 0, int $increment = 1): FibonacciNumber
     {
diff --git a/src/hmmmath/Fibonacci/FibonacciNumber.php b/src/hmmmath/Fibonacci/FibonacciNumber.php
index 71bbe1c..6432563 100644
--- a/src/hmmmath/Fibonacci/FibonacciNumber.php
+++ b/src/hmmmath/Fibonacci/FibonacciNumber.php
@@ -3,8 +3,8 @@
 
 class FibonacciNumber
 {
-    private $start;
-    private $increment;
+    private int $start;
+    private int $increment;
 
     public function __construct(int $start, int $increment)
     {
diff --git a/src/hmmmath/Fibonacci/FibonacciSequence.php b/src/hmmmath/Fibonacci/FibonacciSequence.php
index 8602d4f..4827128 100644
--- a/src/hmmmath/Fibonacci/FibonacciSequence.php
+++ b/src/hmmmath/Fibonacci/FibonacciSequence.php
@@ -5,50 +5,70 @@
 use Iterator;
 use hmmmath\Exception\BadMethodCallException;
 
+
+/**
+ * @implements Iterator<int, FibonacciNumber>
+ * @implements ArrayAccess<int, FibonacciNumber>
+ */
 class FibonacciSequence implements Iterator, ArrayAccess
 {
     /** @var FibonacciNumber */
-    private $number;
+    private FibonacciNumber $number;
 
     /** @var FibonacciNumber */
-    private $initial;
+    private FibonacciNumber $initial;
 
     /** @var int */
-    private $key = 0;
+    private int $key = 0;
 
     public function __construct(int $start = 0, int $increment = 1)
     {
         $this->number = $this->initial = new FibonacciNumber($start, $increment);
     }
 
-    public function current(): int
+	/**
+	 * @return int
+	 */
+	public function current(): int
     {
         return $this->number->getCurrent();
     }
 
-    public function key(): int
+	/**
+	 * @return int
+	 */
+	public function key(): int
     {
         return $this->key;
     }
 
-    public function valid(): bool
+	/**
+	 * @return bool
+	 */
+	public function valid(): bool
     {
         return true;
     }
 
-    public function rewind(): void
+	/**
+	 * @return void
+	 */
+	public function rewind(): void
     {
         $this->key = 0;
         $this->number = $this->initial;
     }
 
-    public function next(): void
+	/**
+	 * @return void
+	 */
+	public function next(): void
     {
         ++$this->key;
         $this->number = $this->number->getNext();
     }
 
-    public function offsetExists($offset): bool // @codingStandardsIgnoreLine
+	public function offsetExists($offset): bool // @codingStandardsIgnoreLine
     {
         return true;
     }
@@ -64,7 +84,7 @@ public function offsetGet($offset): int // @codingStandardsIgnoreLine
         return $number->getCurrent();
     }
 
-    public function offsetSet($offset, $value): void // @codingStandardsIgnoreLine
+	public function offsetSet($offset, $value): void // @codingStandardsIgnoreLine
     {
         throw BadMethodCallException::invalidMethod(__CLASS__, __FUNCTION__);
     }
diff --git a/src/hmmmath/Percentile/Percentile.php b/src/hmmmath/Percentile/Percentile.php
index 03e4332..8355600 100644
--- a/src/hmmmath/Percentile/Percentile.php
+++ b/src/hmmmath/Percentile/Percentile.php
@@ -19,7 +19,7 @@ public static function percentile(
         string $mode = self::NEAREST_RANK,
         bool $sort = true
     ): float {
-        InvalidArgumentException::assertParameterType('2', 'double', $percentile, '0..1');
+        InvalidArgumentException::assertParameterType(2, 'double', $percentile, '0..1');
 
         if ($sort) {
             sort($numbers);