diff --git a/.github/workflows/phpstan.yml b/.github/workflows/phpstan.yml
index 6a1bdf3..513d14d 100644
--- a/.github/workflows/phpstan.yml
+++ b/.github/workflows/phpstan.yml
@@ -20,7 +20,7 @@ jobs:
             -   name: Setup PHP
                 uses: shivammathur/setup-php@v2
                 with:
-                    php-version: '7.2'
+                    php-version: '7.4'
                     coverage: none
                     tools: composer:v2
 
diff --git a/composer.json b/composer.json
index a234679..7dd17fa 100644
--- a/composer.json
+++ b/composer.json
@@ -39,7 +39,7 @@
     },
     "config": {
         "platform": {
-            "php": "7.2"
+            "php": "7.4"
         }
     },
     "repositories": [
diff --git a/phpstan.neon b/phpstan.neon
index 5264ea6..1712066 100644
--- a/phpstan.neon
+++ b/phpstan.neon
@@ -3,7 +3,7 @@ includes:
 
 parameters:
     # Level 5 is a good balance between strictness and practicality
-    level: 5
+    level: 6
 
     # Paths to analyze
     paths:
@@ -20,7 +20,7 @@ parameters:
         # Add specific error patterns to ignore here if needed
 
     # PHP version (must be an integer)
-    phpVersion: 70200
+    phpVersion: 70400
 
     # Treat missing return types as mixed
     treatPhpDocTypesAsCertain: false
diff --git a/src/Config.php b/src/Config.php
index 73cd527..2147e66 100644
--- a/src/Config.php
+++ b/src/Config.php
@@ -48,7 +48,7 @@ class Config
      *
      * @param ContainerInterface $container
      */
-    public static function setServiceContainer($container)
+    public static function setServiceContainer($container): void
     {
         self::$container = $container;
     }
@@ -74,7 +74,7 @@ public static function getHookPrefix(): string
     /**
      * @since 1.0.0
      */
-    public static function setHookPrefix(string $prefix)
+    public static function setHookPrefix(string $prefix): void
     {
         self::$hookPrefix = $prefix;
     }
@@ -105,7 +105,7 @@ public static function getValidationExceptionClass(): string
      *
      * @param class-string<ValidationException> $validationExceptionClass
      */
-    public static function setValidationExceptionClass(string $validationExceptionClass)
+    public static function setValidationExceptionClass(string $validationExceptionClass): void
     {
         if (!is_a($validationExceptionClass, ValidationExceptionInterface::class, true)) {
             throw new RuntimeException(
@@ -142,7 +142,7 @@ public static function getInvalidArgumentExceptionClass(): string
      *
      * @param class-string<InvalidArgumentException> $invalidArgumentExceptionClass
      */
-    public static function setInvalidArgumentExceptionClass(string $invalidArgumentExceptionClass)
+    public static function setInvalidArgumentExceptionClass(string $invalidArgumentExceptionClass): void
     {
         if (!is_a($invalidArgumentExceptionClass, InvalidArgumentException::class, true)) {
             throw new RuntimeException(
diff --git a/src/Contracts/ValidatesOnFrontEnd.php b/src/Contracts/ValidatesOnFrontEnd.php
index 428c97c..8795519 100644
--- a/src/Contracts/ValidatesOnFrontEnd.php
+++ b/src/Contracts/ValidatesOnFrontEnd.php
@@ -11,7 +11,7 @@ interface ValidatesOnFrontEnd
      *
      * @since 1.0.0
      *
-     * @return int|float|string|bool|array|null
+     * @return mixed
      */
     public function serializeOption();
 }
diff --git a/src/Contracts/ValidationRule.php b/src/Contracts/ValidationRule.php
index 0861542..e13107d 100644
--- a/src/Contracts/ValidationRule.php
+++ b/src/Contracts/ValidationRule.php
@@ -34,6 +34,11 @@ public static function fromString(?string $options = null): ValidationRule;
      * @since 1.2.0 add ExcludeValue return option
      * @since 1.0.0
      *
+     * @param mixed $value
+     * @param Closure $fail
+     * @param string $key
+     * @param array<string, mixed> $values
+     *
      * @return void|ExcludeValue|SkipValidationRules
      */
     public function __invoke($value, Closure $fail, string $key, array $values);
diff --git a/src/Rules/Abstracts/ConditionalRule.php b/src/Rules/Abstracts/ConditionalRule.php
index a9fa3d8..f95cd59 100644
--- a/src/Rules/Abstracts/ConditionalRule.php
+++ b/src/Rules/Abstracts/ConditionalRule.php
@@ -5,9 +5,9 @@
 namespace StellarWP\Validation\Rules\Abstracts;
 
 use StellarWP\FieldConditions\ComplexConditionSet;
+use StellarWP\FieldConditions\SimpleConditionSet;
 use StellarWP\FieldConditions\Contracts\Condition;
 use StellarWP\FieldConditions\Contracts\ConditionSet;
-use StellarWP\FieldConditions\SimpleConditionSet;
 use StellarWP\Validation\Config;
 use StellarWP\Validation\Contracts\ValidatesOnFrontEnd;
 use StellarWP\Validation\Contracts\ValidationRule;
@@ -15,12 +15,12 @@
 abstract class ConditionalRule implements ValidationRule, ValidatesOnFrontEnd
 {
     /**
-     * @var ConditionSet
+     * @var SimpleConditionSet|ComplexConditionSet
      */
-    protected $conditions;
+    protected ConditionSet $conditions;
 
     /**
-     * @param ConditionSet|Condition[] $conditions
+     * @param SimpleConditionSet|ComplexConditionSet|Condition[] $conditions
      */
     public function __construct($conditions)
     {
diff --git a/src/Rules/In.php b/src/Rules/In.php
index 768de92..a84ef7f 100644
--- a/src/Rules/In.php
+++ b/src/Rules/In.php
@@ -10,9 +10,9 @@
 class In implements ValidationRule, ValidatesOnFrontEnd
 {
     /**
-     * @var array
+     * @var array<mixed>
      */
-    protected $acceptedValues;
+    protected array $acceptedValues;
 
     /**
      * @since 1.2.0
@@ -24,6 +24,8 @@ public static function id(): string
 
     /**
      * @since 1.2.0
+     *
+     * @param mixed ...$acceptedValues
      */
     final public function __construct(...$acceptedValues)
     {
@@ -64,6 +66,8 @@ public function __invoke($value, Closure $fail, string $key, array $values)
 
     /**
      * @since 1.2.0
+     *
+     * @return array<mixed>
      */
     public function serializeOption(): array
     {
diff --git a/src/ServiceProvider.php b/src/ServiceProvider.php
index 9a0a043..93a86e6 100644
--- a/src/ServiceProvider.php
+++ b/src/ServiceProvider.php
@@ -28,7 +28,10 @@
 
 class ServiceProvider
 {
-    private $validationRules = [
+    /**
+     * @var array<class-string>
+     */
+    private array $validationRules = [
         Required::class,
         Min::class,
         Max::class,
@@ -55,7 +58,7 @@ class ServiceProvider
     /**
      * Registers the validation rules registrar with the container
      */
-    public function register()
+    public function register(): void
     {
         Config::getServiceContainer()->singleton(ValidationRulesRegistrar::class, function () {
             $register = new ValidationRulesRegistrar();
diff --git a/src/ValidationRuleSet.php b/src/ValidationRuleSet.php
index e06b158..ff09f27 100644
--- a/src/ValidationRuleSet.php
+++ b/src/ValidationRuleSet.php
@@ -15,17 +15,17 @@
 use StellarWP\Validation\Contracts\ValidationRule;
 use Traversable;
 
+/**
+ * @implements IteratorAggregate<int, ValidationRule|Closure>
+ */
 class ValidationRuleSet implements IteratorAggregate, JsonSerializable
 {
-    /**
-     * @var ValidationRulesRegistrar
-     */
-    private $register;
+    private ValidationRulesRegistrar $register;
 
     /**
      * @var array<int, ValidationRule|Closure>
      */
-    private $rules = [];
+    private array $rules = [];
 
     /**
      * @since 1.0.0
@@ -168,6 +168,8 @@ public function removeRuleWithId(string $id): self
      * Returns the validation rules.
      *
      * @since 1.0.0
+     *
+     * @return array<int, ValidationRule|Closure>
      */
     public function getRules(): array
     {
diff --git a/src/ValidationRulesRegistrar.php b/src/ValidationRulesRegistrar.php
index 92109d9..5cceda1 100644
--- a/src/ValidationRulesRegistrar.php
+++ b/src/ValidationRulesRegistrar.php
@@ -11,8 +11,10 @@
  */
 class ValidationRulesRegistrar
 {
-    /** @var array */
-    protected $rules = [];
+    /**
+     * @var array<string, class-string<ValidationRule>>
+     */
+    protected array $rules = [];
 
     /**
      * Register one or many validation rules.
diff --git a/src/Validator.php b/src/Validator.php
index 8c22e9f..fc727f6 100644
--- a/src/Validator.php
+++ b/src/Validator.php
@@ -7,6 +7,8 @@
 use StellarWP\Validation\Commands\ExcludeValue;
 use StellarWP\Validation\Commands\SkipValidationRules;
 use StellarWP\Validation\Contracts\Sanitizer;
+use StellarWP\Validation\Contracts\ValidationRule;
+use Closure;
 
 /**
  * A tool for taking in a set of values and corresponding validation rules, and then validating the values.
@@ -18,38 +20,39 @@ class Validator
     /**
      * @var array<string, ValidationRuleSet>
      */
-    private $ruleSets;
+    private array $ruleSets;
 
     /**
      * @var array<string, mixed>
      */
-    private $values;
+    private array $values;
 
     /**
      * @var array<string, string>
      */
-    private $labels;
+    private array $labels;
 
     /**
      * @var array<string, string>
      */
-    private $errors = [];
+    private array $errors = [];
 
     /**
      * @var array<string, mixed>
      */
-    private $validatedValues = [];
+    private array $validatedValues = [];
 
     /**
      * @var bool
      */
-    private $ranValidationRules = false;
+    private bool $ranValidationRules = false;
 
     /**
      * @since 1.0.0
      *
-     * @param array<string, ValidationRuleSet|array> $ruleSets
+     * @param array<string, ValidationRuleSet|array<string|ValidationRule|Closure>> $ruleSets
      * @param array<string, mixed> $values
+     * @param array<string, string> $labels
      */
     public function __construct(array $ruleSets, array $values, array $labels = [])
     {
@@ -98,10 +101,8 @@ public function passes(): bool
      * Will run only once, and then store the results for subsequent calls.
      *
      * @since 1.0.0
-     *
-     * @return void
      */
-    private function runValidationRules()
+    private function runValidationRules(): void
     {
         if ($this->ranValidationRules) {
             return;
@@ -156,6 +157,8 @@ public function errors(): array
      * Returns the validated values, with any sanitization rules applied.
      *
      * @since 1.0.0
+     *
+     * @return array<string, mixed>
      */
     public function validated(): array
     {