diff --git a/src/Input.php b/src/Input.php
index 266fa7f..6fe3b04 100644
--- a/src/Input.php
+++ b/src/Input.php
@@ -16,6 +16,10 @@
 use Gt\Input\InputData\FileUploadInputData;
 use Gt\Input\InputData\QueryStringInputData;
 
+/**
+ * @implements ArrayAccess<string, ?string>
+ * @implements Iterator<string, ?string>
+ */
 class Input implements ArrayAccess, Countable, Iterator {
 	use InputValueGetter;
 	use KeyValueArrayAccess;
@@ -27,14 +31,16 @@ class Input implements ArrayAccess, Countable, Iterator {
 	const DATA_FILES = "files";
 	const DATA_COMBINED = "combined";
 
-	/** @var BodyStream */
-	protected $bodyStream;
-
-	/** @var QueryStringInputData */
-	protected $queryStringParameters;
-	/** @var BodyInputData */
-	protected $bodyParameters;
+	protected BodyStream $bodyStream;
+	protected QueryStringInputData $queryStringParameters;
+	protected BodyInputData $bodyParameters;
 
+	/**
+	 * @param array<string, string> $get
+	 * @param array<string, string> $post
+	 * @param array<string, array<string, string>> $files
+	 * @param string $bodyPath
+	 */
 	public function __construct(
 		array $get = [],
 		array $post = [],
@@ -89,7 +95,6 @@ public function add(string $key, InputDatum $datum, string $method):void {
 
 		default:
 			throw new InvalidInputMethodException($method);
-			break;
 		}
 
 		$this->parameters = new CombinedInputData(
@@ -217,8 +222,10 @@ public function do(string $match):Trigger {
 	 *
 	 * $matches is an associative array, where the key is a request variable's name and the
 	 * value is the request variable's value to match.
+	 *
+	 * @param array<string, string>|string $matches
 	 */
-	public function when(...$matches):Trigger {
+	public function when(array|string...$matches):Trigger {
 		$trigger = new Trigger($this);
 		$trigger->when($matches);
 		return $trigger;
@@ -251,7 +258,7 @@ public function withAll():Trigger {
 		return $this->newTrigger("withAll");
 	}
 
-	protected function newTrigger(string $functionName, ...$args):Trigger {
+	protected function newTrigger(string $functionName, string...$args):Trigger {
 		$trigger = new Trigger($this);
 		return $trigger->$functionName(...$args);
 	}
diff --git a/src/InputData/AbstractInputData.php b/src/InputData/AbstractInputData.php
index 6e31ecf..fd6e610 100644
--- a/src/InputData/AbstractInputData.php
+++ b/src/InputData/AbstractInputData.php
@@ -7,6 +7,10 @@
 use Iterator;
 use Gt\Input\InputData\Datum\InputDatum;
 
+/**
+ * @implements ArrayAccess<string, string|InputDatum>
+ * @implements Iterator<string, string|InputDatum>
+ */
 abstract class AbstractInputData implements ArrayAccess, Countable, Iterator {
 	use InputValueGetter;
 	use KeyValueArrayAccess;
@@ -33,12 +37,12 @@ public function hasValue(string $key):bool {
 	}
 
 	protected function set(string $key, InputDatum $value):void {
-		$this->parameters[$key] = $value;
+		$this->parameters[$key] = (string)$value;
 	}
 
-	public function withKeyValue(string $key, InputDatum $value):self {
+	public function withKeyValue(string $key, InputDatum $value):static {
 		$clone = clone($this);
-		$clone->parameters[$key] = $value;
+		$clone->parameters[$key] = (string)$value;
 		return $clone;
 	}
 }
diff --git a/src/InputData/Datum/FailedFileUpload.php b/src/InputData/Datum/FailedFileUpload.php
index a3dfe1d..213b025 100644
--- a/src/InputData/Datum/FailedFileUpload.php
+++ b/src/InputData/Datum/FailedFileUpload.php
@@ -2,7 +2,7 @@
 namespace Gt\Input\InputData\Datum;
 
 class FailedFileUpload extends FileUpload {
-	protected $errorCode;
+	protected int $errorCode;
 
 	public function __construct(
 		string $originalFilename,
@@ -68,4 +68,4 @@ public function getErrorMessage():string {
 
 		return $msg;
 	}
-}
\ No newline at end of file
+}
diff --git a/src/InputData/Datum/FileUpload.php b/src/InputData/Datum/FileUpload.php
index 4816643..25aeacd 100644
--- a/src/InputData/Datum/FileUpload.php
+++ b/src/InputData/Datum/FileUpload.php
@@ -111,7 +111,7 @@ public function getStream():StreamInterface {
 	 * @throws \RuntimeException on any error during the move operation, or on
 	 *     the second or subsequent call to the method.
 	 */
-	public function moveTo($targetPath) {
+	public function moveTo($targetPath):void {
 		if(!is_uploaded_file($this->tempFilePath)) {
 			throw new UploadedFileSecurityException($this->tempFilePath);
 		}
@@ -195,4 +195,4 @@ public function getClientFilename() {
 	public function getClientMediaType() {
 		return $this->getMimeType();
 	}
-}
\ No newline at end of file
+}
diff --git a/src/InputData/Datum/InputDatum.php b/src/InputData/Datum/InputDatum.php
index b0d44e0..18d7d38 100644
--- a/src/InputData/Datum/InputDatum.php
+++ b/src/InputData/Datum/InputDatum.php
@@ -2,13 +2,13 @@
 namespace Gt\Input\InputData\Datum;
 
 class InputDatum {
-	protected $value;
+	protected mixed $value;
 
-	public function __construct($value) {
+	public function __construct(mixed $value) {
 		$this->value = $value;
 	}
 
 	public function __toString():string {
 		return $this->value;
 	}
-}
\ No newline at end of file
+}
diff --git a/src/InputData/Datum/MultipleInputDatum.php b/src/InputData/Datum/MultipleInputDatum.php
index 0205605..c9cb638 100644
--- a/src/InputData/Datum/MultipleInputDatum.php
+++ b/src/InputData/Datum/MultipleInputDatum.php
@@ -5,10 +5,14 @@
 use Gt\Input\ImmutableObjectModificationException;
 use Iterator;
 
+/**
+ * @implements ArrayAccess<string|int, mixed>
+ * @implements Iterator<string|int, mixed>
+ */
 class MultipleInputDatum extends InputDatum implements ArrayAccess, Iterator {
-	protected $iteratorKey;
+	protected int $iteratorKey;
 
-	public function __construct($value) {
+	public function __construct(mixed $value) {
 		parent::__construct($value);
 
 		$this->iteratorKey = 0;
@@ -18,6 +22,7 @@ public function __toString():string {
 		return implode(", ", $this->value);
 	}
 
+	/** @return array<string, string> */
 	public function toArray():array {
 		$array = [];
 
@@ -64,14 +69,14 @@ public function rewind():void {
 	}
 
 	/** @link http://php.net/manual/en/arrayaccess.offsetexists.php
-	 * @param string $offset
+	 * @param string|int $offset
 	 */
 	public function offsetExists($offset):bool {
 		return isset($this->value[$offset]);
 	}
 
 	/** @link http://php.net/manual/en/arrayaccess.offsetget.php
-	 * @param string $offset
+	 * @param string|int $offset
 	 */
 	public function offsetGet($offset):mixed {
 		return $this->value[$offset];
@@ -79,7 +84,7 @@ public function offsetGet($offset):mixed {
 
 	/**
 	 * @link http://php.net/manual/en/arrayaccess.offsetset.php
-	 * @param string $offset
+	 * @param string|int $offset
 	 * @param string $value
 	 */
 	public function offsetSet($offset, $value):void {
@@ -88,6 +93,7 @@ public function offsetSet($offset, $value):void {
 
 	/**
 	 * @link http://php.net/manual/en/arrayaccess.offsetunset.php
+	 * @param string|int $offset
 	 */
 	public function offsetUnset($offset):void {
 		throw new ImmutableObjectModificationException();
diff --git a/src/InputData/FileUploadInputData.php b/src/InputData/FileUploadInputData.php
index 87736d9..84f39ac 100644
--- a/src/InputData/FileUploadInputData.php
+++ b/src/InputData/FileUploadInputData.php
@@ -5,7 +5,9 @@
 use Gt\Input\InputData\Datum\FileUpload;
 
 class FileUploadInputData extends InputData {
-
+	/**
+	 * @param array<string, string|array<string, string>> $files
+	 */
 	public function __construct(array $files) {
 		$files = $this->normalizeArray($files);
 		$data = $this->createData($files);
@@ -22,8 +24,11 @@ public function __construct(array $files) {
 	 * + size
 	 * Each key's value is string, unless the request parameter name ends with [], in which case
 	 * each value is another array. This function normalises the array to the latter.
+	 *
+	 * @param array<string, string|array<string, string>> $files
+	 * @return array<string, array<string, array<string>>>
 	 */
-	protected function normalizeArray($files):array {
+	protected function normalizeArray(array $files):array {
 		foreach($files as $parameterName => $fileDetailArray) {
 			foreach($fileDetailArray as $key => $value) {
 				if(!is_array($value)) {
@@ -35,6 +40,10 @@ protected function normalizeArray($files):array {
 		return $files;
 	}
 
+	/**
+	 * @param array<string, array<string, array<string>>> $files
+	 * @return array<string, array<FileUpload>>
+	 */
 	protected function createData(array $files):array {
 		$datumList = [];
 
@@ -49,15 +58,22 @@ protected function createData(array $files):array {
 					$details["tmp_name"][$i],
 				];
 
-				if($details["error"][$i] === UPLOAD_ERR_OK) {
-					$datumList[$inputName] []= new FileUpload(...$params);
+				if($details["error"][$i] == UPLOAD_ERR_OK) {
+					array_push(
+						$datumList[$inputName],
+						new FileUpload(...$params)
+					);
 				}
 				else {
 					$params []= (int)$details["error"][$i];
-					$datumList[$inputName] []= new FailedFileUpload(...$params);
+					array_push(
+						$datumList[$inputName],
+						new FailedFileUpload(...$params)
+					);
 				}
 			}
 		}
+
 		return $datumList;
 	}
-}
\ No newline at end of file
+}
diff --git a/src/InputData/InputData.php b/src/InputData/InputData.php
index 7ad7135..b33017d 100644
--- a/src/InputData/InputData.php
+++ b/src/InputData/InputData.php
@@ -6,6 +6,7 @@
 use Gt\Input\InputValueGetter;
 
 class InputData extends AbstractInputData {
+	/** @param iterable<string,string>|iterable<string, array<string>>|iterable<InputData>...$sources */
 	public function __construct(iterable...$sources) {
 		$this->parameters = [];
 
@@ -15,7 +16,7 @@ public function __construct(iterable...$sources) {
 				&& isset($value[0])) {
 					$value = new MultipleInputDatum($value);
 				}
-				else if(!$value instanceof InputDatum) {
+				else {
 					$value = new InputDatum($value);
 				}
 				$this->add($key, $value);
@@ -53,10 +54,12 @@ public function removeExcept(string...$keys):self {
 		return $this;
 	}
 
+	/** @return array<string> */
 	public function getKeys():array {
 		return array_keys($this->parameters);
 	}
 
+	/** @return array<string, string|array<string>> */
 	public function asArray():array {
 		$array = [];
 
diff --git a/src/InputData/InputDataFactory.php b/src/InputData/InputDataFactory.php
index 6d8720f..c337d02 100644
--- a/src/InputData/InputDataFactory.php
+++ b/src/InputData/InputDataFactory.php
@@ -5,6 +5,10 @@
 use Gt\Input\WithWithoutClashingException;
 
 class InputDataFactory {
+	/**
+	 * @param array<string>|array<string, string> $with
+	 * @param array<string>|array<string, string> $without
+	 */
 	public static function create(Input $input, array $with = [], array $without = []):InputData {
 		$data = $input->getAll();
 
@@ -34,4 +38,4 @@ public static function create(Input $input, array $with = [], array $without = [
 
 		return $data;
 	}
-}
\ No newline at end of file
+}
diff --git a/src/InputData/KeyValueArrayAccess.php b/src/InputData/KeyValueArrayAccess.php
index 78c7e8c..7102f83 100644
--- a/src/InputData/KeyValueArrayAccess.php
+++ b/src/InputData/KeyValueArrayAccess.php
@@ -13,7 +13,7 @@ public function offsetGet($offset):mixed {
 		if($this instanceof FileUploadInputData) {
 			return $this->getFile($offset);
 		}
-		elseif($this instanceof Input || $this instanceof InputData) {
+		elseif(is_a($this, Input::class) || is_a($this, InputData::class)) {
 			if($this->contains($offset)) {
 				return $this->get($offset);
 			}
@@ -22,6 +22,10 @@ public function offsetGet($offset):mixed {
 		return null;
 	}
 
+	/**
+	 * @param string $offset
+	 * @param string|InputDatum $value
+	 */
 	public function offsetSet($offset, $value):void {
 		if($this->parameters instanceof InputData) {
 			if(is_string($value)) {
diff --git a/src/InputValueGetter.php b/src/InputValueGetter.php
index a6fe3f2..c399505 100644
--- a/src/InputValueGetter.php
+++ b/src/InputValueGetter.php
@@ -13,10 +13,9 @@
 use TypeError;
 
 trait InputValueGetter {
-	/** @var FileUploadInputData */
-	protected $fileUploadParameters;
-	/** @var CombinedInputData */
-	protected $parameters;
+	protected FileUploadInputData $fileUploadParameters;
+	/** @var array<string, string>|CombinedInputData */
+	protected array|CombinedInputData $parameters;
 
 	public function getString(string $key):?string {
 		return $this->get($key);
@@ -69,9 +68,7 @@ public function getFile(string $key):FileUpload {
 		}
 	}
 
-	/**
-	 * @return FileUpload[]
-	 */
+	/** @return MultipleInputDatum<FileUpload> */
 	public function getMultipleFile(string $key):MultipleInputDatum {
 		return $this->get($key);
 	}
@@ -104,9 +101,7 @@ public function getDateTime(
 		return $dateTime;
 	}
 
-	/**
-	 * @return DateTime[]
-	 */
+	/** @return MultipleInputDatum<DateTime> */
 	public function getMultipleDateTime(string $key):MultipleInputDatum {
 		return $this->get($key);
 	}
diff --git a/src/Trigger/Callback.php b/src/Trigger/Callback.php
index 5ff3e7b..1d95134 100644
--- a/src/Trigger/Callback.php
+++ b/src/Trigger/Callback.php
@@ -6,9 +6,10 @@
 class Callback {
 	/** @var callable */
 	private $callback;
-	private $args;
+	/** @var array<string> */
+	private array $args;
 
-	public function __construct(callable $callback, ...$args) {
+	public function __construct(callable $callback, string...$args) {
 		$this->callback = $callback;
 		$this->args = $args;
 	}
@@ -23,4 +24,4 @@ public function call(InputData $data):void {
 
 		call_user_func_array($this->callback, $parameters);
 	}
-}
\ No newline at end of file
+}
diff --git a/src/Trigger/Trigger.php b/src/Trigger/Trigger.php
index 466e8bd..3112270 100644
--- a/src/Trigger/Trigger.php
+++ b/src/Trigger/Trigger.php
@@ -6,17 +6,19 @@
 use Gt\Input\InputData\InputDataFactory;
 
 class Trigger {
-	/** @var Input */
-	protected $input;
-
-	protected $matches;
-	protected $keyMatches;
-	protected $with;
-	protected $without;
-	/** @var Callback[] */
-	protected $callbacks;
-	/** @var ?bool */
-	protected $hasFired;
+	protected Input $input;
+
+	/** @var array<array<string>> */
+	protected array $matches;
+	/** @var array<string> */
+	protected array $keyMatches;
+	/** @var array<string> */
+	protected array $with;
+	/** @var array<string> */
+	protected array $without;
+	/** @var array<Callback> */
+	protected array $callbacks;
+	protected ?bool $hasFired;
 
 	public function __construct(Input $input) {
 		$this->input = $input;
@@ -29,7 +31,8 @@ public function __construct(Input $input) {
 		$this->hasFired = null;
 	}
 
-	public function when(...$matches):self {
+	/** @param string|array<string, string>...$matches */
+	public function when(string|array...$matches):self {
 		$matches = $this->flattenArray($matches);
 
 		foreach($matches as $key => $match) {
@@ -85,13 +88,13 @@ protected function setKeyTrigger(string $key):self {
 		return $this;
 	}
 
-	public function call(callable $callback, ...$args):self {
+	public function call(callable $callback, string...$args):self {
 		$this->callbacks []= new Callback($callback, ...$args);
 		$this->hasFired = $this->fire();
 		return $this;
 	}
 
-	public function or(callable $callback, ...$args):self {
+	public function or(callable $callback, string...$args):self {
 		if(is_null($this->hasFired)) {
 			throw new CallOrOutOfSequenceException();
 		}
@@ -134,7 +137,7 @@ public function fire():bool {
 		return $fired;
 	}
 
-	protected function callCallbacks() {
+	protected function callCallbacks():void {
 		$fields = InputDataFactory::create(
 			$this->input,
 			$this->with,
@@ -147,6 +150,10 @@ protected function callCallbacks() {
 		}
 	}
 
+	/**
+	 * @param array<string, string|array<string|int, string|array<string|int, string>>> $array
+	 * @return array<string|int, string>
+	 */
 	protected function flattenArray(array $array):array {
 		$result = [];
 
@@ -179,4 +186,4 @@ protected function flattenArray(array $array):array {
 
 		return $result;
 	}
-}
\ No newline at end of file
+}