diff --git a/README.md b/README.md
index 6c136a9..f6ba963 100644
--- a/README.md
+++ b/README.md
@@ -17,7 +17,7 @@ Read more about it at [jsonapi.org](https://jsonapi.org/).
 composer require alsvanzelf/jsonapi
 ```
 
-The library supports, and is is tested on, php versions 5.6, 7 and 8.
+The library requires php 8.2. For lower versions see [v2](/releases/tag/v2.5.0).
 
 #### Upgrading from v1
 
diff --git a/composer.json b/composer.json
index d244643..95de189 100644
--- a/composer.json
+++ b/composer.json
@@ -13,7 +13,7 @@
 		}
 	],
 	"require": {
-		"php": ">=5.6",
+		"php": ">=8.2",
 		"ext-json": "*"
 	},
 	"autoload": {
diff --git a/composer.lock b/composer.lock
index 59b7f8a..c3d435c 100644
--- a/composer.lock
+++ b/composer.lock
@@ -4,7 +4,7 @@
         "Read more about it at https://getcomposer.org/doc/01-basic-usage.md#installing-dependencies",
         "This file is @generated automatically"
     ],
-    "content-hash": "263d00c16803c650bac943c2a0287fcf",
+    "content-hash": "5a2e5669cfe43c78a4d50be96e5dc550",
     "packages": [],
     "packages-dev": [
         {
@@ -2176,7 +2176,7 @@
     "prefer-stable": false,
     "prefer-lowest": false,
     "platform": {
-        "php": ">=5.6",
+        "php": ">=8.2",
         "ext-json": "*"
     },
     "platform-dev": {},
diff --git a/examples/bootstrap_examples.php b/examples/bootstrap_examples.php
index 33abef7..98d2a93 100644
--- a/examples/bootstrap_examples.php
+++ b/examples/bootstrap_examples.php
@@ -92,14 +92,13 @@ public static function findEntities($type) {
 }
 
 class ExampleUser {
-	public $id;
 	public $name;
 	public $heads;
 	public $unknown;
 	
-	public function __construct($id) {
-		$this->id = $id;
-	}
+	public function __construct(
+		public $id,
+	) {}
 	
 	function getCurrentLocation() {
 		return 'Earth';
diff --git a/rector.php b/rector.php
index 03c18b2..f49a0df 100644
--- a/rector.php
+++ b/rector.php
@@ -26,7 +26,7 @@
 	->withIndent(indentChar: "\t", indentSize: 1)
 
 	// slowly increase php version
-	->withPhpSets(php56: true)
+	->withPhpSets(php82: true)
 
 	// slowly increase levels
 	->withTypeCoverageLevel(1)
diff --git a/src/DataDocument.php b/src/DataDocument.php
index a1667c1..470fcef 100644
--- a/src/DataDocument.php
+++ b/src/DataDocument.php
@@ -41,7 +41,7 @@ public function addIncludedResourceObject(ResourceObject ...$resourceObjects) {
 			try {
 				$this->validator->claimUsedResourceIdentifier($resourceObject);
 			}
-			catch (DuplicateException $e) {
+			catch (DuplicateException) {
 				// silently skip duplicates
 				continue;
 			}
diff --git a/src/Document.php b/src/Document.php
index be79032..cd26fcc 100644
--- a/src/Document.php
+++ b/src/Document.php
@@ -288,7 +288,7 @@ public function toArray() {
 	public function toJson(array $options=[]) {
 		$options = array_merge(self::$defaults, $options);
 		
-		$array = ($options['array'] !== null) ? $options['array'] : $this->toArray();
+		$array = $options['array'] ?? $this->toArray();
 		
 		if ($options['prettyPrint']) {
 			$options['encodeOptions'] |= JSON_PRETTY_PRINT;
@@ -314,7 +314,7 @@ public function sendResponse(array $options=[]) {
 			return;
 		}
 		
-		$json = ($options['json'] !== null) ? $options['json'] : $this->toJson($options);
+		$json = $options['json'] ?? $this->toJson($options);
 		
 		http_response_code($this->httpStatusCode);
 		
diff --git a/src/ErrorsDocument.php b/src/ErrorsDocument.php
index 4a8b4d1..69163db 100644
--- a/src/ErrorsDocument.php
+++ b/src/ErrorsDocument.php
@@ -44,17 +44,11 @@ public function __construct(?ErrorObject $errorObject=null) {
 	 */
 	
 	/**
-	 * @param  \Exception|\Throwable $exception
+	 * @param  \Throwable $exception
 	 * @param  array                 $options   optional {@see ErrorsDocument::$defaults}
 	 * @return ErrorsDocument
-	 * 
-	 * @throws InputException if $exception is not \Exception or \Throwable
 	 */
-	public static function fromException($exception, array $options=[]) {
-		if ($exception instanceof \Exception === false && $exception instanceof \Throwable === false) {
-			throw new InputException('input is not a real exception in php5 or php7');
-		}
-		
+	public static function fromException(\Throwable $exception, array $options=[]) {
 		$options = array_merge(self::$defaults, $options);
 		
 		$errorsDocument = new self();
@@ -68,16 +62,10 @@ public static function fromException($exception, array $options=[]) {
 	 * 
 	 * recursively adds multiple ErrorObjects if $exception carries a ->getPrevious()
 	 * 
-	 * @param \Exception|\Throwable $exception
+	 * @param \Throwable $exception
 	 * @param array                 $options   optional {@see ErrorsDocument::$defaults}
-	 * 
-	 * @throws InputException if $exception is not \Exception or \Throwable
 	 */
-	public function addException($exception, array $options=[]) {
-		if ($exception instanceof \Exception === false && $exception instanceof \Throwable === false) {
-			throw new InputException('input is not a real exception in php5 or php7');
-		}
-		
+	public function addException(\Throwable $exception, array $options=[]) {
 		$options = array_merge(self::$defaults, $options);
 		
 		$this->addErrorObject(ErrorObject::fromException($exception, $options));
@@ -152,7 +140,7 @@ public function toArray() {
 	 */
 	protected function determineHttpStatusCode($httpStatusCode) {
 		// add the new code
-		$category = substr($httpStatusCode, 0, 1);
+		$category = substr((string) $httpStatusCode, 0, 1);
 		$this->httpStatusCodes[$category][$httpStatusCode] = true;
 		
 		$advisedStatusCode = $httpStatusCode;
diff --git a/src/helpers/AtMemberManager.php b/src/helpers/AtMemberManager.php
index fbc8b7c..78cbf3e 100644
--- a/src/helpers/AtMemberManager.php
+++ b/src/helpers/AtMemberManager.php
@@ -22,7 +22,7 @@ trait AtMemberManager {
 	 * @param mixed  $value
 	 */
 	public function addAtMember($key, $value) {
-		if (strpos($key, '@') === 0) {
+		if (str_starts_with($key, '@')) {
 			$key = substr($key, 1);
 		}
 		
diff --git a/src/helpers/ExtensionMemberManager.php b/src/helpers/ExtensionMemberManager.php
index 4261628..1bfd257 100644
--- a/src/helpers/ExtensionMemberManager.php
+++ b/src/helpers/ExtensionMemberManager.php
@@ -26,7 +26,7 @@ trait ExtensionMemberManager {
 	public function addExtensionMember(ExtensionInterface $extension, $key, $value) {
 		$namespace = $extension->getNamespace();
 		
-		if (strpos($key, $namespace.':') === 0) {
+		if (str_starts_with($key, $namespace.':')) {
 			$key = substr($key, strlen($namespace.':'));
 		}
 		
diff --git a/src/helpers/RequestParser.php b/src/helpers/RequestParser.php
index d65b180..b672ff7 100644
--- a/src/helpers/RequestParser.php
+++ b/src/helpers/RequestParser.php
@@ -24,23 +24,17 @@ class RequestParser {
 		 */
 		'useAnnotatedSortFields' => true,
 	];
-	/** @var string */
-	private $selfLink = '';
-	/** @var array */
-	private $queryParameters = [];
-	/** @var array */
-	private $document = [];
 	
 	/**
 	 * @param string $selfLink        the uri used to make this request {@see getSelfLink()}
 	 * @param array  $queryParameters all query parameters defined by the specification
 	 * @param array  $document        the request jsonapi document
 	 */
-	public function __construct($selfLink='', array $queryParameters=[], array $document=[]) {
-		$this->selfLink        = $selfLink;
-		$this->queryParameters = $queryParameters;
-		$this->document        = $document;
-	}
+	public function __construct(
+		private $selfLink='',
+		private array $queryParameters=[],
+		private array $document=[],
+	) {}
 	
 	/**
 	 * @return self
@@ -55,8 +49,8 @@ public static function fromSuperglobals() {
 		
 		$document = $_POST;
 		if ($document === [] && isset($_SERVER['CONTENT_TYPE'])) {
-			$documentIsJsonapi = (strpos($_SERVER['CONTENT_TYPE'], Document::CONTENT_TYPE_OFFICIAL) !== false);
-			$documentIsJson    = (strpos($_SERVER['CONTENT_TYPE'], Document::CONTENT_TYPE_DEBUG)    !== false);
+			$documentIsJsonapi = (str_contains((string) $_SERVER['CONTENT_TYPE'], Document::CONTENT_TYPE_OFFICIAL));
+			$documentIsJson    = (str_contains((string) $_SERVER['CONTENT_TYPE'], Document::CONTENT_TYPE_DEBUG));
 			
 			if ($documentIsJsonapi || $documentIsJson) {
 				$document = json_decode(file_get_contents('php://input'), true);
@@ -131,7 +125,7 @@ public function getIncludePaths(array $options=[]) {
 			return [];
 		}
 		
-		$includePaths = explode(',', $this->queryParameters['include']);
+		$includePaths = explode(',', (string) $this->queryParameters['include']);
 		
 		$options = array_merge(self::$defaults, $options);
 		if ($options['useNestedIncludePaths'] === false) {
@@ -171,7 +165,7 @@ public function getSparseFieldset($type) {
 			return [];
 		}
 		
-		return explode(',', $this->queryParameters['fields'][$type]);
+		return explode(',', (string) $this->queryParameters['fields'][$type]);
 	}
 	
 	/**
@@ -200,7 +194,7 @@ public function getSortFields(array $options=[]) {
 			return [];
 		}
 		
-		$fields = explode(',', $this->queryParameters['sort']);
+		$fields = explode(',', (string) $this->queryParameters['sort']);
 		
 		$options = array_merge(self::$defaults, $options);
 		if ($options['useAnnotatedSortFields'] === false) {
@@ -211,7 +205,7 @@ public function getSortFields(array $options=[]) {
 		foreach ($fields as $field) {
 			$order = RequestParser::SORT_ASCENDING;
 			
-			if (strpos($field, '-') === 0) {
+			if (str_starts_with($field, '-')) {
 				$field = substr($field, 1);
 				$order = RequestParser::SORT_DESCENDING;
 			}
diff --git a/src/objects/ErrorObject.php b/src/objects/ErrorObject.php
index 29e9ae7..f0fc317 100644
--- a/src/objects/ErrorObject.php
+++ b/src/objects/ErrorObject.php
@@ -63,22 +63,16 @@ public function __construct($genericCode=null, $genericTitle=null, $specificDeta
 	 */
 	
 	/**
-	 * @param  \Exception|\Throwable $exception
-	 * @param  array                 $options   optional {@see ErrorObject::$defaults}
+	 * @param  \Throwable $exception
+	 * @param  array      $options   optional {@see ErrorObject::$defaults}
 	 * @return ErrorObject
-	 * 
-	 * @throws InputException if $exception is not \Exception or \Throwable
 	 */
-	public static function fromException($exception, array $options=[]) {
-		if ($exception instanceof \Exception === false && $exception instanceof \Throwable === false) {
-			throw new InputException('input is not a real exception in php5 or php7');
-		}
-		
+	public static function fromException(\Throwable $exception, array $options=[]) {
 		$options = array_merge(self::$defaults, $options);
 		
 		$errorObject = new self();
 		
-		$className = get_class($exception);
+		$className = $exception::class;
 		if (strpos($className, '\\')) {
 			$exploded  = explode('\\', $className);
 			$className = end($exploded);
@@ -91,7 +85,7 @@ public static function fromException($exception, array $options=[]) {
 		}
 		
 		$metaObject = MetaObject::fromArray([
-			'type'    => get_class($exception),
+			'type'    => $exception::class,
 			'message' => $exception->getMessage(),
 			'code'    => $exception->getCode(),
 			'file'    => $filePath,
diff --git a/tests/ErrorsDocumentTest.php b/tests/ErrorsDocumentTest.php
index d7be29b..151f44e 100644
--- a/tests/ErrorsDocumentTest.php
+++ b/tests/ErrorsDocumentTest.php
@@ -5,7 +5,6 @@
 use PHPUnit\Framework\Attributes\DataProvider;
 use PHPUnit\Framework\TestCase;
 use alsvanzelf\jsonapi\ErrorsDocument;
-use alsvanzelf\jsonapi\exceptions\InputException;
 use alsvanzelf\jsonapi\objects\ErrorObject;
 
 class ErrorsDocumentTest extends TestCase {
@@ -32,9 +31,6 @@ public function testFromException_HappyPath() {
 		$this->assertSame(self::class, $array['errors'][0]['meta']['trace'][0]['class']);
 	}
 	
-	/**
-	 * @group non-php5
-	 */
 	public function testFromException_AllowsThrowable() {
 		$document = ErrorsDocument::fromException(new \Error('foo', 42));
 		
@@ -58,12 +54,6 @@ public function testFromException_AllowsThrowable() {
 		$this->assertSame(self::class, $array['errors'][0]['meta']['trace'][0]['class']);
 	}
 	
-	public function testFromException_BlocksNonException() {
-		$this->expectException(InputException::class);
-		
-		ErrorsDocument::fromException(new \stdClass());
-	}
-	
 	public function testAddException_WithPrevious() {
 		$exception = new \Exception('foo', 1, new \Exception('bar', 2));
 		
@@ -98,14 +88,6 @@ public function testAddException_SkipPrevious() {
 		$this->assertSame('foo', $array['errors'][0]['meta']['message']);
 	}
 	
-	public function testAddException_BlocksNonException() {
-		$document = new ErrorsDocument();
-		
-		$this->expectException(InputException::class);
-		
-		$document->addException(new \stdClass());
-	}
-	
 	public function testToArray_EmptyErrorObject() {
 		$document = new ErrorsDocument();
 		$document->addErrorObject(new ErrorObject('foo'));
@@ -127,7 +109,6 @@ public function testDetermineHttpStatusCode_HappyPath(int $expectedAdvisedErrorC
 		$document = new ErrorsDocument();
 		
 		$method = new \ReflectionMethod($document, 'determineHttpStatusCode');
-		$method->setAccessible(true);
 		
 		$advisedErrorCode = null;
 		foreach ($allErrorCodes as $errorCode) {
diff --git a/tests/ValidatorTest.php b/tests/ValidatorTest.php
index 8fbdd55..0a373c6 100644
--- a/tests/ValidatorTest.php
+++ b/tests/ValidatorTest.php
@@ -86,7 +86,7 @@ public function testClearUsedFields_FreesForAnotherNamespace() {
 			$objectContainer = Validator::OBJECT_CONTAINER_RELATIONSHIPS;
 			$validator->claimUsedFields($fieldNames, $objectContainer);
 		}
-		catch (DuplicateException $e) {
+		catch (DuplicateException) {
 			$thrown = true;
 		}
 		$this->assertTrue($thrown);
diff --git a/tests/example_output/ExampleUser.php b/tests/example_output/ExampleUser.php
index 4228214..5f342d7 100644
--- a/tests/example_output/ExampleUser.php
+++ b/tests/example_output/ExampleUser.php
@@ -3,14 +3,13 @@
 namespace alsvanzelf\jsonapiTests\example_output;
 
 class ExampleUser {
-	public $id;
 	public $name;
 	public $heads;
 	public $unknown;
 	
-	public function __construct($id) {
-		$this->id = $id;
-	}
+	public function __construct(
+		public $id,
+	) {}
 	
 	function getCurrentLocation() {
 		return 'Earth';
diff --git a/tests/helpers/TestableNonInterfaceRequestInterface.php b/tests/helpers/TestableNonInterfaceRequestInterface.php
index 9bfbd07..e2d26da 100644
--- a/tests/helpers/TestableNonInterfaceRequestInterface.php
+++ b/tests/helpers/TestableNonInterfaceRequestInterface.php
@@ -9,15 +9,11 @@
 use Psr\Http\Message\UriInterface;
 
 class TestableNonInterfaceRequestInterface implements RequestInterface {
-	protected $selfLink;
-	protected $queryParameters;
-	protected $document;
-	
-	public function __construct($selfLink, $queryParameters, $document) {
-		$this->selfLink        = $selfLink;
-		$this->queryParameters = $queryParameters;
-		$this->document        = $document;
-	}
+	public function __construct(
+		protected $selfLink,
+		protected $queryParameters,
+		protected $document,
+	) {}
 	
 	/**
 	 * RequestInterface
diff --git a/tests/helpers/TestableNonInterfaceStreamInterface.php b/tests/helpers/TestableNonInterfaceStreamInterface.php
index fb36096..79f22ca 100644
--- a/tests/helpers/TestableNonInterfaceStreamInterface.php
+++ b/tests/helpers/TestableNonInterfaceStreamInterface.php
@@ -5,11 +5,9 @@
 use Psr\Http\Message\StreamInterface;
 
 class TestableNonInterfaceStreamInterface implements StreamInterface {
-	protected $document;
-	
-	public function __construct($document) {
-		$this->document = $document;
-	}
+	public function __construct(
+		protected $document,
+	) {}
 	
 	/**
 	 * StreamInterface
@@ -24,7 +22,7 @@ public function getContents() {
 	}
 	
 	// not used in current implementation
-	public function __toString() {
+	public function __toString(): string {
 		return '';
 	}
 	
diff --git a/tests/helpers/TestableNonInterfaceUriInterface.php b/tests/helpers/TestableNonInterfaceUriInterface.php
index bdb9af8..aad6bd1 100644
--- a/tests/helpers/TestableNonInterfaceUriInterface.php
+++ b/tests/helpers/TestableNonInterfaceUriInterface.php
@@ -5,13 +5,10 @@
 use Psr\Http\Message\UriInterface;
 
 class TestableNonInterfaceUriInterface implements UriInterface {
-	protected $selfLink;
-	protected $queryParameters;
-	
-	public function __construct($selfLink, $queryParameters) {
-		$this->selfLink        = $selfLink;
-		$this->queryParameters = $queryParameters;
-	}
+	public function __construct(
+		protected $selfLink,
+		protected $queryParameters,
+	) {}
 	
 	/**
 	 * UriInterface
@@ -21,8 +18,8 @@ public function getQuery() {
 		return http_build_query($this->queryParameters);
 	}
 	
-	public function __toString() {
-		return $this->selfLink;
+	public function __toString(): string {
+		return (string) $this->selfLink;
 	}
 	
 	// not used in current implementation
diff --git a/tests/objects/ErrorObjectTest.php b/tests/objects/ErrorObjectTest.php
index 9463a1c..a57fe18 100644
--- a/tests/objects/ErrorObjectTest.php
+++ b/tests/objects/ErrorObjectTest.php
@@ -87,9 +87,6 @@ public function testFromException_NamespacedException() {
 		$this->assertSame('alsvanzelf\jsonapi\exceptions\InputException', $array['meta']['type']);
 	}
 	
-	/**
-	 * @group non-php5
-	 */
 	public function testFromException_NamespacedThrowable() {
 		$exception   = new TestError();
 		$errorObject = ErrorObject::fromException($exception);
@@ -103,12 +100,6 @@ public function testFromException_NamespacedThrowable() {
 		$this->assertSame('alsvanzelf\jsonapiTests\objects\TestError', $array['meta']['type']);
 	}
 	
-	public function testFromException_BlocksNonException() {
-		$this->expectException(InputException::class);
-		
-		ErrorObject::fromException(new \stdClass());
-	}
-	
 	/**
 	 * @deprecated array links are not supported anymore
 	 */
@@ -199,6 +190,4 @@ public function testToArray_WithExtensionMembers() {
 	}
 }
 
-if (PHP_MAJOR_VERSION >= 7) {
-	class TestError extends \Error {}
-}
+class TestError extends \Error {}
diff --git a/tests/profiles/CursorPaginationProfileTest.php b/tests/profiles/CursorPaginationProfileTest.php
index 82ab110..0244a67 100644
--- a/tests/profiles/CursorPaginationProfileTest.php
+++ b/tests/profiles/CursorPaginationProfileTest.php
@@ -319,7 +319,6 @@ public function testGetRangePaginationNotSupportedErrorObject_HappyPath() {
 	public function testSetQueryParameter_HappyPath() {
 		$profile = new CursorPaginationProfile();
 		$method  = new \ReflectionMethod($profile, 'setQueryParameter');
-		$method->setAccessible(true);
 		
 		$url   = '/people?sort=x&page[size]=10&page[after]=foo';
 		$key   = 'page[after]';
@@ -333,7 +332,6 @@ public function testSetQueryParameter_HappyPath() {
 	public function testSetQueryParameter_EncodedUrl() {
 		$profile = new CursorPaginationProfile();
 		$method  = new \ReflectionMethod($profile, 'setQueryParameter');
-		$method->setAccessible(true);
 		
 		$url   = '/people?sort=x&page%5Bsize%5D=10&page%5Bafter%5D=foo';
 		$key   = 'page[after]';