diff --git a/.gitignore b/.gitignore
index 17dcf1d2c..eca67cb16 100644
--- a/.gitignore
+++ b/.gitignore
@@ -29,6 +29,7 @@ composer.phar
 
 # PHP CS Fixer
 /.php-cs-fixer.cache
+/.php-cs-fixer.php
 
 # po4a .mo files
 *.mo
diff --git a/.php-cs-fixer.dist.php b/.php-cs-fixer.dist.php
index c8091220b..7571f3048 100644
--- a/.php-cs-fixer.dist.php
+++ b/.php-cs-fixer.dist.php
@@ -7,16 +7,29 @@
 use PhpCsFixer\Runner\Parallel\ParallelConfigFactory;
 
 $finder = (new Finder())->in([
+    __DIR__ . '/config',
     __DIR__ . '/src',
     __DIR__ . '/tests',
 ]);
 
 return (new Config())
+    ->setRiskyAllowed(true)
     ->setParallelConfig(ParallelConfigFactory::detect())
     ->setRules([
         '@PER-CS3.0' => true,
         'no_unused_imports' => true,
         'ordered_class_elements' => true,
         'class_attributes_separation' => ['elements' => ['method' => 'one']],
+        'declare_strict_types' => true,
+        'native_function_invocation' => true,
+        'native_constant_invocation' => true,
+        'fully_qualified_strict_types' => [
+            'import_symbols' => true
+        ],
+        'global_namespace_import' => [
+            'import_classes' => true,
+            'import_constants' => true,
+            'import_functions' => true,
+        ],
     ])
     ->setFinder($finder);
diff --git a/CHANGELOG.md b/CHANGELOG.md
index bf4f07aeb..983283a7c 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,7 +2,7 @@
 
 ## 2.5.2 under development
 
-- no changes in this release.
+- Enh #787: Explicitly import classes, functions, and constants in "use" section (@mspirkov)
 
 ## 2.5.1 December 12, 2025
 
diff --git a/config/di.php b/config/di.php
index ccaa6ee6f..7ec3d6575 100644
--- a/config/di.php
+++ b/config/di.php
@@ -25,10 +25,10 @@
     'yii.validator.categorySource' => [
         'definition' => static function () use ($params): CategorySource {
             $reader = class_exists(MessageSource::class)
-                ? new MessageSource(dirname(__DIR__) . '/messages')
+                ? new MessageSource(\dirname(__DIR__) . '/messages')
                 : new IdMessageReader(); // @codeCoverageIgnore
 
-            $formatter = extension_loaded('intl')
+            $formatter = \extension_loaded('intl')
                 ? new IntlMessageFormatter()
                 : new SimpleMessageFormatter();
 
diff --git a/src/Debug/ValidatorCollector.php b/src/Debug/ValidatorCollector.php
index af4b3febd..303e787c2 100644
--- a/src/Debug/ValidatorCollector.php
+++ b/src/Debug/ValidatorCollector.php
@@ -9,6 +9,8 @@
 use Yiisoft\Yii\Debug\Collector\CollectorTrait;
 use Yiisoft\Yii\Debug\Collector\SummaryCollectorInterface;
 
+use function count;
+
 final class ValidatorCollector implements SummaryCollectorInterface
 {
     use CollectorTrait;
diff --git a/src/Exception/InvalidCallbackReturnTypeException.php b/src/Exception/InvalidCallbackReturnTypeException.php
index fc90a26f6..bedd4056b 100644
--- a/src/Exception/InvalidCallbackReturnTypeException.php
+++ b/src/Exception/InvalidCallbackReturnTypeException.php
@@ -11,6 +11,8 @@
 use Yiisoft\Validator\Rule\Callback;
 use Yiisoft\Validator\Rule\CallbackHandler;
 
+use function sprintf;
+
 /**
  * An exception used by the handler ({@see CallbackHandler}) of {@see Callback} rule for the cases when returned value
  * is not a {@see Result} instance.
diff --git a/src/Exception/RuleHandlerInterfaceNotImplementedException.php b/src/Exception/RuleHandlerInterfaceNotImplementedException.php
index 2f843c6d7..9c25a751a 100644
--- a/src/Exception/RuleHandlerInterfaceNotImplementedException.php
+++ b/src/Exception/RuleHandlerInterfaceNotImplementedException.php
@@ -10,6 +10,8 @@
 use Yiisoft\Validator\RuleHandlerInterface;
 use Yiisoft\Validator\RuleHandlerResolverInterface;
 
+use function sprintf;
+
 /**
  * An exception used by {@see RuleHandlerResolverInterface} implementations (e. g., {@see RuleHandlerContainer}) for
  * the case when a retrieved value is not an object or an object that does not implement {@see RuleHandlerInterface}.
diff --git a/src/Exception/RuleHandlerNotFoundException.php b/src/Exception/RuleHandlerNotFoundException.php
index 6013c24a1..3d7e114c5 100644
--- a/src/Exception/RuleHandlerNotFoundException.php
+++ b/src/Exception/RuleHandlerNotFoundException.php
@@ -8,6 +8,8 @@
 use Throwable;
 use Yiisoft\Validator\RuleHandlerResolver\RuleHandlerContainer;
 
+use function sprintf;
+
 /**
  * An exception used by {@see RuleHandlerContainer} for the case when a given class name was not found in the container.
  */
diff --git a/src/Exception/UnexpectedRuleException.php b/src/Exception/UnexpectedRuleException.php
index ba1300a78..88ed3be7a 100644
--- a/src/Exception/UnexpectedRuleException.php
+++ b/src/Exception/UnexpectedRuleException.php
@@ -7,6 +7,8 @@
 use InvalidArgumentException;
 use Throwable;
 
+use function sprintf;
+
 /**
  * An exception used by rule handlers to guarantee that passed rule have desired type. Every handler's validation code
  * must start with this check. An example for `MyRule` and `MyRuleHandler`:
diff --git a/src/Helper/ObjectParser.php b/src/Helper/ObjectParser.php
index 15d778bad..cf841c9f8 100644
--- a/src/Helper/ObjectParser.php
+++ b/src/Helper/ObjectParser.php
@@ -22,6 +22,7 @@
 use function is_int;
 use function is_object;
 use function is_string;
+use function sprintf;
 
 /**
  * A helper class used to parse rules from PHP attributes (attached to class properties and class itself) and data from
diff --git a/src/Helper/RulesDumper.php b/src/Helper/RulesDumper.php
index df534cbdd..af9c649ba 100644
--- a/src/Helper/RulesDumper.php
+++ b/src/Helper/RulesDumper.php
@@ -10,6 +10,7 @@
 
 use function is_int;
 use function is_string;
+use function sprintf;
 
 /**
  * RulesDumper allows to get an array of rule names and corresponding settings from a set of rules.
diff --git a/src/Helper/RulesNormalizer.php b/src/Helper/RulesNormalizer.php
index 966765434..5c79c3b0f 100644
--- a/src/Helper/RulesNormalizer.php
+++ b/src/Helper/RulesNormalizer.php
@@ -17,6 +17,8 @@
 use function is_callable;
 use function is_int;
 use function is_string;
+use function is_object;
+use function sprintf;
 
 /**
  * A helper class used to normalize different types of data to the iterable with rule instances ({@see RuleInterface}).
diff --git a/src/Helper/RulesNormalizerIterator.php b/src/Helper/RulesNormalizerIterator.php
index c4d2324ac..678e6c6e7 100644
--- a/src/Helper/RulesNormalizerIterator.php
+++ b/src/Helper/RulesNormalizerIterator.php
@@ -12,6 +12,7 @@
 use Yiisoft\Validator\SkipOnEmptyInterface;
 
 use function is_callable;
+use function sprintf;
 
 /**
  * An iterator for a set of rules, performs normalization for every individual rule unifying other provided types and
diff --git a/src/Rule/AbstractCompare.php b/src/Rule/AbstractCompare.php
index 037e96b6c..7fdbcf6e3 100644
--- a/src/Rule/AbstractCompare.php
+++ b/src/Rule/AbstractCompare.php
@@ -17,6 +17,7 @@
 use Yiisoft\Validator\WhenInterface;
 
 use function in_array;
+use function is_scalar;
 
 /**
  * Abstract base for all the comparison validation rules.
diff --git a/src/Rule/BooleanValueHandler.php b/src/Rule/BooleanValueHandler.php
index bd23a92e2..c0735ebfa 100644
--- a/src/Rule/BooleanValueHandler.php
+++ b/src/Rule/BooleanValueHandler.php
@@ -10,6 +10,8 @@
 use Yiisoft\Validator\RuleInterface;
 use Yiisoft\Validator\ValidationContext;
 
+use function is_scalar;
+
 /**
  * A handler for {@see BooleanValue} rule.
  */
diff --git a/src/Rule/Callback.php b/src/Rule/Callback.php
index 28857e79c..ee1d8ac39 100644
--- a/src/Rule/Callback.php
+++ b/src/Rule/Callback.php
@@ -17,6 +17,8 @@
 use Yiisoft\Validator\SkipOnErrorInterface;
 use Yiisoft\Validator\WhenInterface;
 
+use function sprintf;
+
 /**
  * Defines validation options to validating the value using a callback.
  *
diff --git a/src/Rule/CompareHandler.php b/src/Rule/CompareHandler.php
index 11559668b..a010f582d 100644
--- a/src/Rule/CompareHandler.php
+++ b/src/Rule/CompareHandler.php
@@ -14,6 +14,9 @@
 use Yiisoft\Validator\ValidationContext;
 
 use function gettype;
+use function is_scalar;
+
+use const PHP_FLOAT_EPSILON;
 
 /**
  * Compares the specified value with "target" value provided directly or within a property.
diff --git a/src/Rule/Count.php b/src/Rule/Count.php
index 57bd440ab..93bdcb9bd 100644
--- a/src/Rule/Count.php
+++ b/src/Rule/Count.php
@@ -47,7 +47,7 @@ final class Count implements
      * @param int|null $max Maximum number of items. null means no maximum number limit. Can't be combined with
      * {@see $exactly}. See {@see $greaterThanMaxMessage} for the customized message for a value with too many items.
      * @param string $incorrectInputMessage Error message used when the value is neither an array nor an object
-     * implementing {@see \Countable} interface.
+     * implementing {@see Countable} interface.
      *
      * You may use the following placeholders in the message:
      *
@@ -117,7 +117,7 @@ public function getName(): string
     }
 
     /**
-     * Get error message used when the value is neither an array nor an object implementing {@see \Countable} interface.
+     * Get error message used when the value is neither an array nor an object implementing {@see Countable} interface.
      *
      * @return string Error message.
      *
diff --git a/src/Rule/Date/BaseDateHandler.php b/src/Rule/Date/BaseDateHandler.php
index f8ad75e56..03dc33dea 100644
--- a/src/Rule/Date/BaseDateHandler.php
+++ b/src/Rule/Date/BaseDateHandler.php
@@ -15,6 +15,9 @@
 use Yiisoft\Validator\RuleInterface;
 use Yiisoft\Validator\ValidationContext;
 
+use function is_int;
+use function is_string;
+
 /**
  * @see Date
  * @see DateTime
diff --git a/src/Rule/Image/ImageHandler.php b/src/Rule/Image/ImageHandler.php
index a82251bc7..6248f1777 100644
--- a/src/Rule/Image/ImageHandler.php
+++ b/src/Rule/Image/ImageHandler.php
@@ -13,6 +13,8 @@
 
 use function is_string;
 
+use const UPLOAD_ERR_OK;
+
 /**
  * Validates that a value is an image and optionally checks its dimensions.
  *
diff --git a/src/Rule/InEnum.php b/src/Rule/InEnum.php
index 993edeae4..1577782c3 100644
--- a/src/Rule/InEnum.php
+++ b/src/Rule/InEnum.php
@@ -17,6 +17,8 @@
 use Yiisoft\Validator\SkipOnErrorInterface;
 use Yiisoft\Validator\WhenInterface;
 
+use function sprintf;
+
 /**
  * Defines validation options to check that the value is one of the values (or names) contained in an enum of the
  * specified class.
diff --git a/src/Rule/JsonHandler.php b/src/Rule/JsonHandler.php
index 354339830..6e3c880a5 100644
--- a/src/Rule/JsonHandler.php
+++ b/src/Rule/JsonHandler.php
@@ -13,6 +13,8 @@
 use function function_exists;
 use function is_string;
 
+use const JSON_ERROR_NONE;
+
 /**
  * A handler for {@see Json} rule. Validates that the value is a valid JSON string.
  *
diff --git a/src/Rule/Nested.php b/src/Rule/Nested.php
index e72c4b33a..bfe62aefa 100644
--- a/src/Rule/Nested.php
+++ b/src/Rule/Nested.php
@@ -36,6 +36,7 @@
 use function ltrim;
 use function rtrim;
 use function sprintf;
+use function is_callable;
 
 /**
  * Used to define rules for validation of nested structures:
diff --git a/src/Rule/NumberHandler.php b/src/Rule/NumberHandler.php
index e83ecd72c..38399d94f 100644
--- a/src/Rule/NumberHandler.php
+++ b/src/Rule/NumberHandler.php
@@ -12,6 +12,7 @@
 use Yiisoft\Validator\ValidationContext;
 
 use function is_bool;
+use function is_scalar;
 
 /**
  * Validates that the value is a number.
diff --git a/src/Rule/TrueValueHandler.php b/src/Rule/TrueValueHandler.php
index b3bde212b..274dc1003 100644
--- a/src/Rule/TrueValueHandler.php
+++ b/src/Rule/TrueValueHandler.php
@@ -10,6 +10,8 @@
 use Yiisoft\Validator\RuleInterface;
 use Yiisoft\Validator\ValidationContext;
 
+use function is_scalar;
+
 /**
  * A handler for {@see TrueValue} rule.
  */
diff --git a/src/Rule/UniqueIterableHandler.php b/src/Rule/UniqueIterableHandler.php
index 929524088..a06cb7a32 100644
--- a/src/Rule/UniqueIterableHandler.php
+++ b/src/Rule/UniqueIterableHandler.php
@@ -14,6 +14,9 @@
 
 use function count;
 use function gettype;
+use function is_scalar;
+
+use const SORT_REGULAR;
 
 /**
  * A handler for {@see UniqueIterable} rule. Validates uniqueness of each element of an iterable.
diff --git a/tests/DataSet/ObjectDataSetTest.php b/tests/DataSet/ObjectDataSetTest.php
index f648158b0..91c4076fa 100644
--- a/tests/DataSet/ObjectDataSetTest.php
+++ b/tests/DataSet/ObjectDataSetTest.php
@@ -37,6 +37,8 @@
 use Yiisoft\Validator\Tests\Support\Data\Charts\Chart;
 use Yiisoft\Validator\Validator;
 
+use function sprintf;
+
 final class ObjectDataSetTest extends TestCase
 {
     public static function propertyVisibilityDataProvider(): array
diff --git a/tests/Rule/CompareTest.php b/tests/Rule/CompareTest.php
index d86dd2135..bc501f23c 100644
--- a/tests/Rule/CompareTest.php
+++ b/tests/Rule/CompareTest.php
@@ -22,6 +22,10 @@
 use Yiisoft\Validator\Tests\Support\Data\CompareObject;
 
 use function is_string;
+use function sprintf;
+
+use const PHP_FLOAT_EPSILON;
+use const PHP_INT_MAX;
 
 final class CompareTest extends RuleTestCase
 {
diff --git a/tests/Rule/Image/ImageTest.php b/tests/Rule/Image/ImageTest.php
index c094bea21..1a93eff25 100644
--- a/tests/Rule/Image/ImageTest.php
+++ b/tests/Rule/Image/ImageTest.php
@@ -20,6 +20,9 @@
 use Yiisoft\Validator\Tests\Rule\Base\WhenTestTrait;
 use Yiisoft\Validator\Validator;
 
+use const UPLOAD_ERR_NO_FILE;
+use const UPLOAD_ERR_OK;
+
 final class ImageTest extends RuleTestCase
 {
     use DifferentRuleInHandlerTestTrait;
diff --git a/tests/Rule/Nested/NestedTest.php b/tests/Rule/Nested/NestedTest.php
index 64572c796..419a27cf6 100644
--- a/tests/Rule/Nested/NestedTest.php
+++ b/tests/Rule/Nested/NestedTest.php
@@ -53,8 +53,10 @@
 use Yiisoft\Validator\Tests\Support\RulesProvider\SimpleRulesProvider;
 use Yiisoft\Validator\ValidationContext;
 use Yiisoft\Validator\Validator;
+use ArrayIterator;
 
 use function array_slice;
+use function in_array;
 
 final class NestedTest extends RuleTestCase
 {
@@ -1538,7 +1540,7 @@ public function testWithNonArrayButIterableOfObjects(): void
             #[Each(new Nested())]
             public iterable $collection;
         };
-        $collection = new \ArrayIterator([$classA]);
+        $collection = new ArrayIterator([$classA]);
         $classB->collection = $collection;
         $result = (new Validator())->validate($classB);
 
diff --git a/tests/Rule/NumberTest.php b/tests/Rule/NumberTest.php
index 495602192..ade27cac4 100644
--- a/tests/Rule/NumberTest.php
+++ b/tests/Rule/NumberTest.php
@@ -16,6 +16,8 @@
 use Yiisoft\Validator\Tests\Rule\Base\SkipOnErrorTestTrait;
 use Yiisoft\Validator\Tests\Rule\Base\WhenTestTrait;
 
+use const PHP_INT_MAX;
+
 final class NumberTest extends RuleTestCase
 {
     use RuleWithOptionsTestTrait;
diff --git a/tests/Support/Data/IteratorWithBooleanKey.php b/tests/Support/Data/IteratorWithBooleanKey.php
index db21028ff..5e3cb9fe7 100644
--- a/tests/Support/Data/IteratorWithBooleanKey.php
+++ b/tests/Support/Data/IteratorWithBooleanKey.php
@@ -7,8 +7,9 @@
 use ReturnTypeWillChange;
 use Yiisoft\Validator\Rule\Length;
 use Yiisoft\Validator\RuleInterface;
+use Iterator;
 
-class IteratorWithBooleanKey implements \Iterator
+class IteratorWithBooleanKey implements Iterator
 {
     private int $position = 0;
     private array $array;
diff --git a/tests/Support/Rule/PiHandler.php b/tests/Support/Rule/PiHandler.php
index 841a4f9c8..126226868 100644
--- a/tests/Support/Rule/PiHandler.php
+++ b/tests/Support/Rule/PiHandler.php
@@ -11,6 +11,9 @@
 
 use function abs;
 
+use const M_PI;
+use const PHP_FLOAT_EPSILON;
+
 final class PiHandler implements RuleHandlerInterface
 {
     public function validate(mixed $value, RuleInterface $rule, ValidationContext $context): Result