diff --git a/phpstan.neon b/phpstan.neon
index b95427a..ef6cdd2 100644
--- a/phpstan.neon
+++ b/phpstan.neon
@@ -11,9 +11,6 @@ parameters:
     paths:
         - src
 
-    scanDirectories:
-        - /usr/share/icinga-php
-
     ignoreErrors:
         -
             messages:
diff --git a/src/BaseFilter.php b/src/BaseFilter.php
index 267decb..0b0a946 100644
--- a/src/BaseFilter.php
+++ b/src/BaseFilter.php
@@ -6,8 +6,8 @@
 
 trait BaseFilter
 {
-    /** @var Rule Base filter */
-    private $baseFilter;
+    /** @var ?Rule Base filter */
+    private ?Rule $baseFilter = null;
 
     /**
      * Get whether a base filter has been set
@@ -24,7 +24,7 @@ public function hasBaseFilter(): bool
      *
      * @return ?Rule
      */
-    public function getBaseFilter()
+    public function getBaseFilter(): ?Rule
     {
         return $this->baseFilter;
     }
@@ -32,11 +32,11 @@ public function getBaseFilter()
     /**
      * Set the base filter
      *
-     * @param Rule $baseFilter
+     * @param ?Rule $baseFilter
      *
      * @return $this
      */
-    public function setBaseFilter(Rule $baseFilter = null): self
+    public function setBaseFilter(?Rule $baseFilter = null): static
     {
         $this->baseFilter = $baseFilter;
 
diff --git a/src/Contract/Filterable.php b/src/Contract/Filterable.php
index 2a6316a..a6fcdb3 100644
--- a/src/Contract/Filterable.php
+++ b/src/Contract/Filterable.php
@@ -11,7 +11,7 @@ interface Filterable
      *
      * @return Filter\Chain
      */
-    public function getFilter();
+    public function getFilter(): Filter\Chain;
 
     /**
      * Add a filter to the query
@@ -23,7 +23,7 @@ public function getFilter();
      *
      * @return $this
      */
-    public function filter(Filter\Rule $filter);
+    public function filter(Filter\Rule $filter): static;
 
     /**
      * Add a filter to the query
@@ -35,7 +35,7 @@ public function filter(Filter\Rule $filter);
      *
      * @return $this
      */
-    public function orFilter(Filter\Rule $filter);
+    public function orFilter(Filter\Rule $filter): static;
 
     /**
      * Add a filter to the query
@@ -47,7 +47,7 @@ public function orFilter(Filter\Rule $filter);
      *
      * @return $this
      */
-    public function notFilter(Filter\Rule $filter);
+    public function notFilter(Filter\Rule $filter): static;
 
     /**
      * Add a filter to the query
@@ -59,5 +59,5 @@ public function notFilter(Filter\Rule $filter);
      *
      * @return $this
      */
-    public function orNotFilter(Filter\Rule $filter);
+    public function orNotFilter(Filter\Rule $filter): static;
 }
diff --git a/src/Contract/Paginatable.php b/src/Contract/Paginatable.php
index 3e2a4ee..07470af 100644
--- a/src/Contract/Paginatable.php
+++ b/src/Contract/Paginatable.php
@@ -11,14 +11,14 @@ interface Paginatable extends Countable
      *
      * @return bool
      */
-    public function hasLimit();
+    public function hasLimit(): bool;
 
     /**
      * Get the limit
      *
      * @return int|null
      */
-    public function getLimit();
+    public function getLimit(): ?int;
 
     /**
      * Set the limit
@@ -28,21 +28,21 @@ public function getLimit();
      *
      * @return $this
      */
-    public function limit($limit);
+    public function limit(?int $limit): static;
 
     /**
      * Get whether an offset is set
      *
      * @return bool
      */
-    public function hasOffset();
+    public function hasOffset(): bool;
 
     /**
      * Get the offset
      *
      * @return int|null
      */
-    public function getOffset();
+    public function getOffset(): ?int;
 
     /**
      * Set the offset
@@ -52,5 +52,5 @@ public function getOffset();
      *
      * @return $this
      */
-    public function offset($offset);
+    public function offset(?int $offset): static;
 }
diff --git a/src/Contract/PluginLoader.php b/src/Contract/PluginLoader.php
index 1be779c..5c5bdd7 100644
--- a/src/Contract/PluginLoader.php
+++ b/src/Contract/PluginLoader.php
@@ -17,5 +17,5 @@ interface PluginLoader
      *
      * @return string|false FQN of the plugin's class if found, false otherwise
      */
-    public function load($name);
+    public function load(string $name): false|string;
 }
diff --git a/src/Contract/Translator.php b/src/Contract/Translator.php
index 85ab515..15ae8f6 100644
--- a/src/Contract/Translator.php
+++ b/src/Contract/Translator.php
@@ -10,25 +10,25 @@ interface Translator
     /**
      * Translate a message
      *
-     * @param string $message
-     * @param string $context Message context
+     * @param string      $message
+     * @param string|null $context Message context
      *
      * @return string Translated message or original message if no translation is found
      */
-    public function translate($message, $context = null);
+    public function translate(string $message, ?string $context = null): string;
 
     /**
      * Translate a message in the given domain
      *
      * If no translation is found in the specified domain, the translation is also searched for in the default domain.
      *
-     * @param string $domain
-     * @param string $message
-     * @param string $context Message context
+     * @param string      $domain
+     * @param string      $message
+     * @param string|null $context Message context
      *
      * @return string Translated message or original message if no translation is found
      */
-    public function translateInDomain($domain, $message, $context = null);
+    public function translateInDomain(string $domain, string $message, ?string $context = null): string;
 
     /**
      * Translate a plural message
@@ -36,14 +36,14 @@ public function translateInDomain($domain, $message, $context = null);
      * The returned message is based on the given number to decide between the singular and plural forms.
      * That is also the case if no translation is found.
      *
-     * @param string $singular Singular message
-     * @param string $plural   Plural message
-     * @param int    $number   Number to decide between the returned singular and plural forms
-     * @param string $context  Message context
+     * @param string      $singular Singular message
+     * @param string      $plural   Plural message
+     * @param int         $number   Number to decide between the returned singular and plural forms
+     * @param string|null $context  Message context
      *
      * @return string Translated message or original message if no translation is found
      */
-    public function translatePlural($singular, $plural, $number, $context = null);
+    public function translatePlural(string $singular, string $plural, int $number, ?string $context = null): string;
 
     /**
      * Translate a plural message in the given domain
@@ -53,13 +53,13 @@ public function translatePlural($singular, $plural, $number, $context = null);
      * The returned message is based on the given number to decide between the singular and plural forms.
      * That is also the case if no translation is found.
      *
-     * @param string $domain
-     * @param string $singular Singular message
-     * @param string $plural   Plural message
-     * @param int    $number   Number to decide between the returned singular and plural forms
-     * @param string $context  Message context
+     * @param string      $domain
+     * @param string      $singular Singular message
+     * @param string      $plural   Plural message
+     * @param int         $number   Number to decide between the returned singular and plural forms
+     * @param string|null $context  Message context
      *
      * @return string Translated message or original message if no translation is found
      */
-    public function translatePluralInDomain($domain, $singular, $plural, $number, $context = null);
+    public function translatePluralInDomain(string $domain, string $singular, string $plural, int $number, ?string $context = null): string;
 }
diff --git a/src/Data.php b/src/Data.php
index b12306c..d54d598 100644
--- a/src/Data.php
+++ b/src/Data.php
@@ -5,14 +5,14 @@
 class Data
 {
     /** @var array<string, mixed> */
-    protected $data = [];
+    protected array $data = [];
 
     /**
      * Check whether there's any data
      *
      * @return bool
      */
-    public function isEmpty()
+    public function isEmpty(): bool
     {
         return empty($this->data);
     }
@@ -24,7 +24,7 @@ public function isEmpty()
      *
      * @return bool
      */
-    public function has($name)
+    public function has(string $name): bool
     {
         return array_key_exists($name, $this->data);
     }
@@ -37,7 +37,7 @@ public function has($name)
      *
      * @return mixed
      */
-    public function get($name, $default = null)
+    public function get(string $name, mixed $default = null): mixed
     {
         if ($this->has($name)) {
             return $this->data[$name];
@@ -54,7 +54,7 @@ public function get($name, $default = null)
      *
      * @return $this
      */
-    public function set($name, $value)
+    public function set(string $name, mixed $value): static
     {
         $this->data[$name] = $value;
 
@@ -68,7 +68,7 @@ public function set($name, $value)
      *
      * @return $this
      */
-    public function merge(self $with)
+    public function merge(self $with): static
     {
         $this->data = array_merge($this->data, $with->data);
 
@@ -80,7 +80,7 @@ public function merge(self $with)
      *
      * @return $this
      */
-    public function clear()
+    public function clear(): static
     {
         $this->data = [];
 
diff --git a/src/Filter.php b/src/Filter.php
index 3bbdd36..c8b9afd 100644
--- a/src/Filter.php
+++ b/src/Filter.php
@@ -36,7 +36,7 @@ protected function __construct()
      *
      * @return bool
      */
-    public static function match(Rule $rule, $row)
+    public static function match(Rule $rule, array|object $row): bool
     {
         if (! is_object($row)) {
             if (is_array($row)) {
@@ -59,7 +59,7 @@ public static function match(Rule $rule, $row)
      *
      * @return Chain
      */
-    public static function all(Rule ...$rules)
+    public static function all(Rule ...$rules): Chain
     {
         return new All(...$rules);
     }
@@ -72,7 +72,7 @@ public static function all(Rule ...$rules)
      *
      * @return bool
      */
-    protected function matchAll(All $rules, $row)
+    protected function matchAll(All $rules, object $row): bool
     {
         foreach ($rules as $rule) {
             if (! $this->performMatch($rule, $row)) {
@@ -90,7 +90,7 @@ protected function matchAll(All $rules, $row)
      *
      * @return Chain
      */
-    public static function any(Rule ...$rules)
+    public static function any(Rule ...$rules): Chain
     {
         return new Any(...$rules);
     }
@@ -103,7 +103,7 @@ public static function any(Rule ...$rules)
      *
      * @return bool
      */
-    protected function matchAny(Any $rules, $row)
+    protected function matchAny(Any $rules, object $row): bool
     {
         foreach ($rules as $rule) {
             if ($this->performMatch($rule, $row)) {
@@ -121,7 +121,7 @@ protected function matchAny(Any $rules, $row)
      *
      * @return Chain
      */
-    public static function none(Rule ...$rules)
+    public static function none(Rule ...$rules): Chain
     {
         return new None(...$rules);
     }
@@ -134,7 +134,7 @@ public static function none(Rule ...$rules)
      *
      * @return bool
      */
-    protected function matchNone(None $rules, $row)
+    protected function matchNone(None $rules, object $row): bool
     {
         foreach ($rules as $rule) {
             if ($this->performMatch($rule, $row)) {
@@ -153,7 +153,7 @@ protected function matchNone(None $rules, $row)
      *
      * @return Condition
      */
-    public static function equal($column, $value)
+    public static function equal(string $column, $value): Condition
     {
         return new Equal($column, $value);
     }
@@ -166,17 +166,8 @@ public static function equal($column, $value)
      *
      * @return bool
      */
-    protected function matchEqual($rule, $row)
+    protected function matchEqual(Equal|Unequal $rule, object $row): bool
     {
-        if (! $rule instanceof Equal && ! $rule instanceof Unequal) {
-            throw new InvalidArgumentException(sprintf(
-                'Rule must be of type %s or %s, got %s instead',
-                Equal::class,
-                Unequal::class,
-                get_php_type($rule)
-            ));
-        }
-
         $rowValue = $this->extractValue($rule->getColumn(), $row);
         $value = $rule->getValue();
         $this->normalizeTypes($rowValue, $value);
@@ -200,11 +191,11 @@ protected function matchEqual($rule, $row)
      * Performs a wildcard search if the value contains asterisks.
      *
      * @param string $column
-     * @param string|string[] $value
+     * @param string|string[]|null $value
      *
      * @return Condition
      */
-    public static function like($column, $value)
+    public static function like(string $column, string|array|null $value): Condition
     {
         return new Like($column, $value);
     }
@@ -217,17 +208,8 @@ public static function like($column, $value)
      *
      * @return bool
      */
-    protected function matchSimilar($rule, $row)
+    protected function matchSimilar(Like|Unlike $rule, object $row): bool
     {
-        if (! $rule instanceof Like && ! $rule instanceof Unlike) {
-            throw new InvalidArgumentException(sprintf(
-                'Rule must be of type %s or %s, got %s instead',
-                Like::class,
-                Unlike::class,
-                get_php_type($rule)
-            ));
-        }
-
         $rowValue = $this->extractValue($rule->getColumn(), $row);
         $value = $rule->getValue();
         $this->normalizeTypes($rowValue, $value);
@@ -254,7 +236,7 @@ protected function matchSimilar($rule, $row)
      *
      * @return bool
      */
-    protected function performEqualityMatch($value, $rowValue, $ignoreCase = false)
+    protected function performEqualityMatch(mixed $value, mixed $rowValue, bool $ignoreCase = false): bool
     {
         if ($ignoreCase && is_string($rowValue)) {
             $rowValue = strtolower($rowValue);
@@ -280,7 +262,7 @@ protected function performEqualityMatch($value, $rowValue, $ignoreCase = false)
      *
      * @return bool
      */
-    protected function performSimilarityMatch($value, $rowValue, $ignoreCase = false)
+    protected function performSimilarityMatch(mixed $value, mixed $rowValue, bool $ignoreCase = false): bool
     {
         if ($ignoreCase && is_string($rowValue)) {
             $rowValue = strtolower($rowValue);
@@ -323,7 +305,7 @@ protected function performSimilarityMatch($value, $rowValue, $ignoreCase = false
      *
      * @return Condition
      */
-    public static function unequal($column, $value)
+    public static function unequal(string $column, $value): Condition
     {
         return new Unequal($column, $value);
     }
@@ -336,7 +318,7 @@ public static function unequal($column, $value)
      *
      * @return bool
      */
-    protected function matchUnequal(Unequal $rule, $row)
+    protected function matchUnequal(Unequal $rule, object $row): bool
     {
         return ! $this->matchEqual($rule, $row);
     }
@@ -347,11 +329,11 @@ protected function matchUnequal(Unequal $rule, $row)
      * Performs a wildcard search if the value contains asterisks.
      *
      * @param string $column
-     * @param string|string[] $value
+     * @param string|string[]|null $value
      *
      * @return Condition
      */
-    public static function unlike($column, $value)
+    public static function unlike(string $column, string|array|null $value): Condition
     {
         return new Unlike($column, $value);
     }
@@ -364,7 +346,7 @@ public static function unlike($column, $value)
      *
      * @return bool
      */
-    protected function matchUnlike(Unlike $rule, $row)
+    protected function matchUnlike(Unlike $rule, object $row): bool
     {
         return ! $this->matchSimilar($rule, $row);
     }
@@ -377,7 +359,7 @@ protected function matchUnlike(Unlike $rule, $row)
      *
      * @return Condition
      */
-    public static function greaterThan($column, $value)
+    public static function greaterThan(string $column, $value): Condition
     {
         return new GreaterThan($column, $value);
     }
@@ -390,7 +372,7 @@ public static function greaterThan($column, $value)
      *
      * @return bool
      */
-    protected function matchGreaterThan(GreaterThan $rule, $row)
+    protected function matchGreaterThan(GreaterThan $rule, object $row): bool
     {
         $rowValue = $this->extractValue($rule->getColumn(), $row);
         $value = $rule->getValue();
@@ -406,7 +388,7 @@ protected function matchGreaterThan(GreaterThan $rule, $row)
      *
      * @return Condition
      */
-    public static function lessThan($column, $value)
+    public static function lessThan(string $column, $value): Condition
     {
         return new LessThan($column, $value);
     }
@@ -419,7 +401,7 @@ public static function lessThan($column, $value)
      *
      * @return bool
      */
-    protected function matchLessThan(LessThan $rule, $row)
+    protected function matchLessThan(LessThan $rule, object $row): bool
     {
         $rowValue = $this->extractValue($rule->getColumn(), $row);
         $value = $rule->getValue();
@@ -435,7 +417,7 @@ protected function matchLessThan(LessThan $rule, $row)
      *
      * @return Condition
      */
-    public static function greaterThanOrEqual($column, $value)
+    public static function greaterThanOrEqual(string $column, $value): Condition
     {
         return new GreaterThanOrEqual($column, $value);
     }
@@ -448,7 +430,7 @@ public static function greaterThanOrEqual($column, $value)
      *
      * @return bool
      */
-    protected function matchGreaterThanOrEqual(GreaterThanOrEqual $rule, $row)
+    protected function matchGreaterThanOrEqual(GreaterThanOrEqual $rule, object $row): bool
     {
         $rowValue = $this->extractValue($rule->getColumn(), $row);
         $value = $rule->getValue();
@@ -464,7 +446,7 @@ protected function matchGreaterThanOrEqual(GreaterThanOrEqual $rule, $row)
      *
      * @return Condition
      */
-    public static function lessThanOrEqual($column, $value)
+    public static function lessThanOrEqual(string $column, $value): Condition
     {
         return new LessThanOrEqual($column, $value);
     }
@@ -477,7 +459,7 @@ public static function lessThanOrEqual($column, $value)
      *
      * @return bool
      */
-    protected function matchLessThanOrEqual(LessThanOrEqual $rule, $row)
+    protected function matchLessThanOrEqual(LessThanOrEqual $rule, object $row): bool
     {
         $rowValue = $this->extractValue($rule->getColumn(), $row);
         $value = $rule->getValue();
@@ -493,37 +475,27 @@ protected function matchLessThanOrEqual(LessThanOrEqual $rule, $row)
      *
      * @return bool
      */
-    protected function performMatch(Rule $rule, $row)
+    protected function performMatch(Rule $rule, object $row): bool
     {
-        switch (true) {
-            case $rule instanceof All:
-                return $this->matchAll($rule, $row);
-            case $rule instanceof Any:
-                return $this->matchAny($rule, $row);
-            case $rule instanceof Like:
-                return $this->matchSimilar($rule, $row);
-            case $rule instanceof Equal:
-                return $this->matchEqual($rule, $row);
-            case $rule instanceof GreaterThan:
-                return $this->matchGreaterThan($rule, $row);
-            case $rule instanceof GreaterThanOrEqual:
-                return $this->matchGreaterThanOrEqual($rule, $row);
-            case $rule instanceof LessThan:
-                return $this->matchLessThan($rule, $row);
-            case $rule instanceof LessThanOrEqual:
-                return $this->matchLessThanOrEqual($rule, $row);
-            case $rule instanceof None:
-                return $this->matchNone($rule, $row);
-            case $rule instanceof Unequal:
-                return $this->matchUnequal($rule, $row);
-            case $rule instanceof Unlike:
-                return $this->matchUnlike($rule, $row);
-            default:
-                throw new InvalidArgumentException(sprintf(
+        return match (true) {
+            $rule instanceof All                => $this->matchAll($rule, $row),
+            $rule instanceof Any                => $this->matchAny($rule, $row),
+            $rule instanceof Like               => $this->matchSimilar($rule, $row),
+            $rule instanceof Equal              => $this->matchEqual($rule, $row),
+            $rule instanceof GreaterThan        => $this->matchGreaterThan($rule, $row),
+            $rule instanceof GreaterThanOrEqual => $this->matchGreaterThanOrEqual($rule, $row),
+            $rule instanceof LessThan           => $this->matchLessThan($rule, $row),
+            $rule instanceof LessThanOrEqual    => $this->matchLessThanOrEqual($rule, $row),
+            $rule instanceof None               => $this->matchNone($rule, $row),
+            $rule instanceof Unequal            => $this->matchUnequal($rule, $row),
+            $rule instanceof Unlike             => $this->matchUnlike($rule, $row),
+            default                             => throw new InvalidArgumentException(
+                sprintf(
                     'Unable to match filter. Rule type %s is unknown',
                     get_class($rule)
-                ));
-        }
+                )
+            ),
+        };
     }
 
     /**
@@ -534,13 +506,9 @@ protected function performMatch(Rule $rule, $row)
      *
      * @return mixed
      */
-    protected function extractValue($column, $row)
+    protected function extractValue(string $column, object $row): mixed
     {
-        try {
-            return $row->{$column};
-        } catch (Throwable $_) {
-            return null;
-        }
+        return $row->$column ?? null;
     }
 
     /**
@@ -554,7 +522,7 @@ protected function extractValue($column, $row)
      *
      * @return void
      */
-    protected function normalizeTypes($rowValue, &$value)
+    protected function normalizeTypes(mixed $rowValue, mixed &$value): void
     {
         if ($rowValue === null || $value === null) {
             return;
diff --git a/src/Filter/Chain.php b/src/Filter/Chain.php
index c0060e6..de153f3 100644
--- a/src/Filter/Chain.php
+++ b/src/Filter/Chain.php
@@ -14,7 +14,7 @@ abstract class Chain implements Rule, MetaDataProvider, IteratorAggregate, Count
     use MetaData;
 
     /** @var array<int, Rule> */
-    protected $rules = [];
+    protected array $rules = [];
 
     /**
      * Create a new Chain
@@ -59,7 +59,7 @@ public function getIterator(): Traversable
      *
      * @return $this
      */
-    public function add(Rule $rule)
+    public function add(Rule $rule): static
     {
         $this->rules[] = $rule;
 
@@ -75,7 +75,7 @@ public function add(Rule $rule)
      * @throws OutOfBoundsException In case no existing rule is found
      * @return $this
      */
-    public function insertBefore(Rule $rule, Rule $before)
+    public function insertBefore(Rule $rule, Rule $before): static
     {
         $ruleAt = array_search($before, $this->rules, true);
         if ($ruleAt === false) {
@@ -96,7 +96,7 @@ public function insertBefore(Rule $rule, Rule $before)
      * @throws OutOfBoundsException In case no existing rule is found
      * @return $this
      */
-    public function insertAfter(Rule $rule, Rule $after)
+    public function insertAfter(Rule $rule, Rule $after): static
     {
         $ruleAt = array_search($after, $this->rules, true);
         if ($ruleAt === false) {
@@ -115,7 +115,7 @@ public function insertAfter(Rule $rule, Rule $after)
      *
      * @return bool
      */
-    public function has(Rule $rule)
+    public function has(Rule $rule): bool
     {
         return array_search($rule, $this->rules, true) !== false;
     }
@@ -129,7 +129,7 @@ public function has(Rule $rule)
      * @throws OutOfBoundsException In case no existing rule is found
      * @return $this
      */
-    public function replace(Rule $rule, Rule $replacement)
+    public function replace(Rule $rule, Rule $replacement): static
     {
         $ruleAt = array_search($rule, $this->rules, true);
         if ($ruleAt === false) {
@@ -148,7 +148,7 @@ public function replace(Rule $rule, Rule $replacement)
      *
      * @return $this
      */
-    public function remove(Rule $rule)
+    public function remove(Rule $rule): static
     {
         $ruleAt = array_search($rule, $this->rules, true);
         if ($ruleAt !== false) {
@@ -163,7 +163,7 @@ public function remove(Rule $rule)
      *
      * @return bool
      */
-    public function isEmpty()
+    public function isEmpty(): bool
     {
         return empty($this->rules);
     }
diff --git a/src/Filter/Condition.php b/src/Filter/Condition.php
index cc35610..dfb160a 100644
--- a/src/Filter/Condition.php
+++ b/src/Filter/Condition.php
@@ -6,19 +6,19 @@ abstract class Condition implements Rule, MetaDataProvider
 {
     use MetaData;
 
-    /** @var string */
-    protected $column;
+    /** @var string|string[] */
+    protected string|array $column = [];
 
     /** @var mixed */
-    protected $value;
+    protected mixed $value = null;
 
     /**
      * Create a new Condition
      *
-     * @param string $column
+     * @param string|string[] $column
      * @param mixed $value
      */
-    public function __construct($column, $value)
+    public function __construct(string|array $column, mixed $value)
     {
         $this->setColumn($column)
             ->setValue($value);
@@ -37,11 +37,11 @@ public function __clone()
     /**
      * Set this condition's column
      *
-     * @param string $column
+     * @param string|string[] $column
      *
      * @return $this
      */
-    public function setColumn($column)
+    public function setColumn(string|array $column): static
     {
         $this->column = $column;
 
@@ -51,9 +51,9 @@ public function setColumn($column)
     /**
      * Get this condition's column
      *
-     * @return string
+     * @return string|string[]
      */
-    public function getColumn()
+    public function getColumn(): string|array
     {
         return $this->column;
     }
@@ -65,7 +65,7 @@ public function getColumn()
      *
      * @return $this
      */
-    public function setValue($value)
+    public function setValue(mixed $value): static
     {
         $this->value = $value;
 
@@ -77,7 +77,7 @@ public function setValue($value)
      *
      * @return mixed
      */
-    public function getValue()
+    public function getValue(): mixed
     {
         return $this->value;
     }
diff --git a/src/Filter/Equal.php b/src/Filter/Equal.php
index 71da490..f5f22de 100644
--- a/src/Filter/Equal.php
+++ b/src/Filter/Equal.php
@@ -5,14 +5,14 @@
 class Equal extends Condition
 {
     /** @var bool */
-    protected $ignoreCase = false;
+    protected bool $ignoreCase = false;
 
     /**
      * Ignore case on both sides of the equation
      *
      * @return $this
      */
-    public function ignoreCase()
+    public function ignoreCase(): static
     {
         $this->ignoreCase = true;
 
@@ -24,7 +24,7 @@ public function ignoreCase()
     *
     * @return bool
     */
-    public function ignoresCase()
+    public function ignoresCase(): bool
     {
         return $this->ignoreCase;
     }
diff --git a/src/Filter/Like.php b/src/Filter/Like.php
index 7a06279..d720c71 100644
--- a/src/Filter/Like.php
+++ b/src/Filter/Like.php
@@ -5,14 +5,14 @@
 class Like extends Condition
 {
     /** @var bool */
-    protected $ignoreCase = false;
+    protected bool $ignoreCase = false;
 
     /**
      * Ignore case on both sides of the equation
      *
      * @return $this
      */
-    public function ignoreCase()
+    public function ignoreCase(): static
     {
         $this->ignoreCase = true;
 
@@ -24,7 +24,7 @@ public function ignoreCase()
     *
     * @return bool
     */
-    public function ignoresCase()
+    public function ignoresCase(): bool
     {
         return $this->ignoreCase;
     }
diff --git a/src/Filter/MetaData.php b/src/Filter/MetaData.php
index 6fe2523..700b2ff 100644
--- a/src/Filter/MetaData.php
+++ b/src/Filter/MetaData.php
@@ -6,10 +6,10 @@
 
 trait MetaData
 {
-    /** @var Data */
-    protected $metaData;
+    /** @var ?Data */
+    protected ?Data $metaData = null;
 
-    public function metaData()
+    public function metaData(): Data
     {
         if ($this->metaData === null) {
             $this->metaData = new Data();
diff --git a/src/Filter/MetaDataProvider.php b/src/Filter/MetaDataProvider.php
index ef9557e..c4f0ab9 100644
--- a/src/Filter/MetaDataProvider.php
+++ b/src/Filter/MetaDataProvider.php
@@ -11,5 +11,5 @@ interface MetaDataProvider
      *
      * @return Data
      */
-    public function metaData();
+    public function metaData(): Data;
 }
diff --git a/src/Filter/Unequal.php b/src/Filter/Unequal.php
index 5e37cbd..7742dfe 100644
--- a/src/Filter/Unequal.php
+++ b/src/Filter/Unequal.php
@@ -5,14 +5,14 @@
 class Unequal extends Condition
 {
     /** @var bool */
-    protected $ignoreCase = false;
+    protected bool $ignoreCase = false;
 
     /**
      * Ignore case on both sides of the equation
      *
      * @return $this
      */
-    public function ignoreCase()
+    public function ignoreCase(): static
     {
         $this->ignoreCase = true;
 
@@ -24,7 +24,7 @@ public function ignoreCase()
     *
     * @return bool
     */
-    public function ignoresCase()
+    public function ignoresCase(): bool
     {
         return $this->ignoreCase;
     }
diff --git a/src/Filter/Unlike.php b/src/Filter/Unlike.php
index 16b9fb3..df8936d 100644
--- a/src/Filter/Unlike.php
+++ b/src/Filter/Unlike.php
@@ -5,14 +5,14 @@
 class Unlike extends Condition
 {
     /** @var bool */
-    protected $ignoreCase = false;
+    protected bool $ignoreCase = false;
 
     /**
      * Ignore case on both sides of the equation
      *
      * @return $this
      */
-    public function ignoreCase()
+    public function ignoreCase(): static
     {
         $this->ignoreCase = true;
 
@@ -24,7 +24,7 @@ public function ignoreCase()
     *
     * @return bool
     */
-    public function ignoresCase()
+    public function ignoresCase(): bool
     {
         return $this->ignoreCase;
     }
diff --git a/src/Filters.php b/src/Filters.php
index defff43..c4b03ad 100644
--- a/src/Filters.php
+++ b/src/Filters.php
@@ -4,15 +4,15 @@
 
 trait Filters
 {
-    /** @var Filter\Chain */
-    protected $filter;
+    /** @var ?Filter\Chain */
+    protected ?Filter\Chain $filter = null;
 
-    public function getFilter()
+    public function getFilter(): Filter\Chain
     {
         return $this->filter ?: Filter::all();
     }
 
-    public function filter(Filter\Rule $filter)
+    public function filter(Filter\Rule $filter): static
     {
         $currentFilter = $this->getFilter();
         if ($currentFilter instanceof Filter\All) {
@@ -27,7 +27,7 @@ public function filter(Filter\Rule $filter)
         return $this;
     }
 
-    public function orFilter(Filter\Rule $filter)
+    public function orFilter(Filter\Rule $filter): static
     {
         $currentFilter = $this->getFilter();
         if ($currentFilter instanceof Filter\Any) {
@@ -42,14 +42,14 @@ public function orFilter(Filter\Rule $filter)
         return $this;
     }
 
-    public function notFilter(Filter\Rule $filter)
+    public function notFilter(Filter\Rule $filter): static
     {
         $this->filter(Filter::none($filter));
 
         return $this;
     }
 
-    public function orNotFilter(Filter\Rule $filter)
+    public function orNotFilter(Filter\Rule $filter): static
     {
         $this->orFilter(Filter::none($filter));
 
diff --git a/src/Loader/AutoloadingPluginLoader.php b/src/Loader/AutoloadingPluginLoader.php
index ba195c6..a9de176 100644
--- a/src/Loader/AutoloadingPluginLoader.php
+++ b/src/Loader/AutoloadingPluginLoader.php
@@ -10,10 +10,10 @@
 class AutoloadingPluginLoader implements PluginLoader
 {
     /** @var string Namespace of the plugins */
-    protected $namespace;
+    protected string $namespace;
 
     /** @var string Class name postfix */
-    protected $postfix;
+    protected string $postfix;
 
     /**
      * Create a new autoloading plugin loader
@@ -21,7 +21,7 @@ class AutoloadingPluginLoader implements PluginLoader
      * @param string $namespace Namespace of the plugins
      * @param string $postfix   Class name postfix
      */
-    public function __construct($namespace, $postfix = '')
+    public function __construct(string $namespace, string $postfix = '')
     {
         $this->namespace = $namespace;
         $this->postfix = $postfix;
@@ -34,12 +34,12 @@ public function __construct($namespace, $postfix = '')
      *
      * @return string
      */
-    protected function getFqn($name)
+    protected function getFqn(string $name): string
     {
         return $this->namespace . '\\' . ucfirst($name) . $this->postfix;
     }
 
-    public function load($name)
+    public function load(string $name): false|string
     {
         $class = $this->getFqn($name);
 
diff --git a/src/Plugins.php b/src/Plugins.php
index a5dbb77..5e9c12b 100644
--- a/src/Plugins.php
+++ b/src/Plugins.php
@@ -23,7 +23,7 @@ public static function wantPluginLoader($loaderOrNamespace, $postfix = '')
         if ($loaderOrNamespace instanceof PluginLoader) {
             $loader = $loaderOrNamespace;
         } else {
-            $loader = new AutoloadingPluginLoader($loaderOrNamespace, $postfix);
+            $loader = new AutoloadingPluginLoader($loaderOrNamespace, $postfix ?? '');
         }
 
         return $loader;
diff --git a/src/PriorityQueue.php b/src/PriorityQueue.php
index 1992ec5..68856d4 100644
--- a/src/PriorityQueue.php
+++ b/src/PriorityQueue.php
@@ -15,7 +15,7 @@
 class PriorityQueue extends SplPriorityQueue
 {
     /** @var int */
-    protected $serial = PHP_INT_MAX;
+    protected int $serial = PHP_INT_MAX;
 
     /**
      * Inserts an element in the queue by sifting it up.
@@ -25,9 +25,9 @@ class PriorityQueue extends SplPriorityQueue
      * @param TValue $value
      * @param TPriority $priority
      *
-     * @return bool
+     * @return true
      */
-    public function insert($value, $priority): bool
+    public function insert($value, $priority): true
     {
         return parent::insert($value, [$priority, $this->serial--]);
     }
@@ -37,7 +37,7 @@ public function insert($value, $priority): bool
      *
      * @return Generator
      */
-    public function yieldAll()
+    public function yieldAll(): Generator
     {
         // Clone queue because the SplPriorityQueue acts as a heap and thus items are removed upon iteration
         $queue = clone $this;
diff --git a/src/Seq.php b/src/Seq.php
index dbae277..14cb755 100644
--- a/src/Seq.php
+++ b/src/Seq.php
@@ -12,13 +12,13 @@ class Seq
     /**
      * Check if the traversable contains the given needle
      *
-     * @param array<mixed>|iterable<mixed> $traversable
+     * @param iterable<mixed> $traversable
      * @param mixed $needle Might also be a closure
      * @param bool $caseSensitive Whether strings should be compared case-sensitive
      *
      * @return bool
      */
-    public static function contains($traversable, $needle, $caseSensitive = true)
+    public static function contains(iterable $traversable, mixed $needle, bool $caseSensitive = true): bool
     {
         return self::find($traversable, $needle, $caseSensitive)[0] !== null;
     }
@@ -26,14 +26,14 @@ public static function contains($traversable, $needle, $caseSensitive = true)
     /**
      * Search in the traversable for the given needle and return its key and value
      *
-     * @param array<mixed>|iterable<mixed> $traversable
+     * @param iterable<mixed> $traversable
      * @param mixed $needle Might also be a closure
      * @param bool $caseSensitive Whether strings should be compared case-sensitive
      *
      * @return array<mixed> An array with two entries, the first is the key, then the value.
      *                      Both are null if nothing is found.
      */
-    public static function find($traversable, $needle, $caseSensitive = true)
+    public static function find(iterable $traversable, mixed $needle, bool $caseSensitive = true): array
     {
         $usesCallback = $needle instanceof Closure;
         if (! $usesCallback && $caseSensitive && is_array($traversable)) {
@@ -66,13 +66,13 @@ public static function find($traversable, $needle, $caseSensitive = true)
     /**
      * Search in the traversable for the given needle and return its key
      *
-     * @param array<mixed>|iterable<mixed> $traversable
+     * @param iterable<mixed> $traversable
      * @param mixed $needle Might also be a closure
      * @param bool $caseSensitive Whether strings should be compared case-sensitive
      *
      * @return mixed|null Null if nothing is found
      */
-    public static function findKey($traversable, $needle, $caseSensitive = true)
+    public static function findKey(iterable $traversable, mixed $needle, bool $caseSensitive = true): mixed
     {
         return self::find($traversable, $needle, $caseSensitive)[0];
     }
@@ -80,13 +80,13 @@ public static function findKey($traversable, $needle, $caseSensitive = true)
     /**
      * Search in the traversable for the given needle and return its value
      *
-     * @param array<mixed>|iterable<mixed> $traversable
+     * @param iterable<mixed> $traversable
      * @param mixed $needle Might also be a closure
      * @param bool $caseSensitive Whether strings should be compared case-sensitive
      *
      * @return mixed|null Null if nothing is found
      */
-    public static function findValue($traversable, $needle, $caseSensitive = true)
+    public static function findValue(iterable $traversable, mixed $needle, bool $caseSensitive = true): mixed
     {
         $usesCallback = $needle instanceof Closure;
         if (! $usesCallback && $caseSensitive && is_array($traversable)) {
diff --git a/src/Str.php b/src/Str.php
index b1cd19c..338ca4a 100644
--- a/src/Str.php
+++ b/src/Str.php
@@ -16,7 +16,7 @@ class Str
      *
      * @return string
      */
-    public static function camel(?string $subject)
+    public static function camel(?string $subject): string
     {
         if ($subject === null) {
             return '';
@@ -36,7 +36,7 @@ public static function camel(?string $subject)
      *
      * @return bool
      */
-    public static function startsWith(?string $subject, string $start, bool $caseSensitive = true)
+    public static function startsWith(?string $subject, string $start, bool $caseSensitive = true): bool
     {
         $subject = $subject ?? '';
         if (! $caseSensitive) {
@@ -58,7 +58,7 @@ public static function startsWith(?string $subject, string $start, bool $caseSen
      *
      * @return array<int, ?string>
      */
-    public static function symmetricSplit(?string $subject, string $delimiter, int $limit, ?string $default = null)
+    public static function symmetricSplit(?string $subject, string $delimiter, int $limit, ?string $default = null): array
     {
         if ($subject === null || empty($delimiter)) {
             return array_pad([], $limit, $default);
@@ -76,7 +76,7 @@ public static function symmetricSplit(?string $subject, string $delimiter, int $
      *
      * @return array<string>
      */
-    public static function trimSplit(?string $subject, string $delimiter = ',', int $limit = null)
+    public static function trimSplit(?string $subject, string $delimiter = ',', ?int $limit = null): array
     {
         if ($subject === null || empty($delimiter)) {
             return [];
diff --git a/src/functions.php b/src/functions.php
index e7f9be0..b455580 100644
--- a/src/functions.php
+++ b/src/functions.php
@@ -17,7 +17,7 @@
  *
  * @return string
  */
-function get_php_type($subject)
+function get_php_type(mixed $subject): string
 {
     if (is_object($subject)) {
         return get_class($subject);
@@ -35,7 +35,7 @@ function get_php_type($subject)
  *
  * @throws InvalidArgumentException If subject type is invalid
  */
-function arrayval($subject)
+function arrayval($subject): array
 {
     if (is_array($subject)) {
         return $subject;
@@ -63,7 +63,7 @@ function arrayval($subject)
  *
  * @return mixed The first key of the iterable if it is not empty, null otherwise
  */
-function iterable_key_first($iterable)
+function iterable_key_first(iterable $iterable): mixed
 {
     foreach ($iterable as $key => $_) {
         return $key;
@@ -79,7 +79,7 @@ function iterable_key_first($iterable)
  *
  * @return ?mixed
  */
-function iterable_value_first($iterable)
+function iterable_value_first(iterable $iterable): mixed
 {
     foreach ($iterable as $_ => $value) {
         return $value;
diff --git a/tests/Loader/TestPluginLoader.php b/tests/Loader/TestPluginLoader.php
index 1ec8f61..8ce4651 100644
--- a/tests/Loader/TestPluginLoader.php
+++ b/tests/Loader/TestPluginLoader.php
@@ -16,7 +16,7 @@ public function __construct($canLoad = true)
         $this->canLoad = $canLoad;
     }
 
-    public function load($name)
+    public function load(string $name): false|string
     {
         if (! $this->canLoad) {
             return false;