diff --git a/src/Rules/Arrays/DuplicateKeysInLiteralArraysRule.php b/src/Rules/Arrays/DuplicateKeysInLiteralArraysRule.php
index a1eaf7e131..89e2d65bb7 100644
--- a/src/Rules/Arrays/DuplicateKeysInLiteralArraysRule.php
+++ b/src/Rules/Arrays/DuplicateKeysInLiteralArraysRule.php
@@ -13,6 +13,8 @@
 use function array_keys;
 use function count;
 use function implode;
+use function is_float;
+use function key;
 use function max;
 use function sprintf;
 use function var_export;
@@ -85,23 +87,24 @@ public function processNode(Node $node, Scope $scope): array
 			}
 
 			$value = $keyType->getValue();
+			$index = is_float($value) ? (int) $value : key([$value => null]);
 			$printedValue = $key !== null
 				? $this->exprPrinter->printExpr($key)
 				: $value;
 
-			$printedValues[$value][] = $printedValue;
+			$printedValues[$index][] = $printedValue;
 
-			if (!isset($valueLines[$value])) {
-				$valueLines[$value] = $item->getStartLine();
+			if (!isset($valueLines[$index])) {
+				$valueLines[$index] = $item->getStartLine();
 			}
 
 			$previousCount = count($values);
-			$values[$value] = $printedValue;
+			$values[$index] = $printedValue;
 			if ($previousCount !== count($values)) {
 				continue;
 			}
 
-			$duplicateKeys[$value] = true;
+			$duplicateKeys[$index] = true;
 		}
 
 		$messages = [];
diff --git a/src/Rules/Arrays/InvalidKeyInArrayDimFetchRule.php b/src/Rules/Arrays/InvalidKeyInArrayDimFetchRule.php
index 1242f85cfd..38bf4f47bb 100644
--- a/src/Rules/Arrays/InvalidKeyInArrayDimFetchRule.php
+++ b/src/Rules/Arrays/InvalidKeyInArrayDimFetchRule.php
@@ -4,6 +4,7 @@
 
 use PhpParser\Node;
 use PHPStan\Analyser\Scope;
+use PHPStan\Php\PhpVersion;
 use PHPStan\Rules\Rule;
 use PHPStan\Rules\RuleErrorBuilder;
 use PHPStan\Rules\RuleLevelHelper;
@@ -22,6 +23,7 @@ class InvalidKeyInArrayDimFetchRule implements Rule
 	public function __construct(
 		private RuleLevelHelper $ruleLevelHelper,
 		private bool $reportMaybes,
+		private PhpVersion $phpVersion,
 	)
 	{
 	}
@@ -54,15 +56,34 @@ public function processNode(Node $node, Scope $scope): array
 		}
 
 		$isSuperType = AllowedArrayKeysTypes::getType()->isSuperTypeOf($dimensionType);
-		if ($isSuperType->yes() || ($isSuperType->maybe() && !$this->reportMaybes)) {
-			return [];
+		$isOk = $isSuperType->yes() || ($isSuperType->maybe() && !$this->reportMaybes);
+		if (!$isOk) {
+			return [
+				RuleErrorBuilder::message(
+					sprintf('%s array key type %s.', $isSuperType->no() ? 'Invalid' : 'Possibly invalid', $dimensionType->describe(VerbosityLevel::typeOnly())),
+				)->identifier('offsetAccess.invalidOffset')->build(),
+			];
+		}
+
+		if ($this->phpVersion->getVersionId() >= 80100) {
+			$isFloat = $dimensionType->isFloat();
+
+			if ($isFloat->yes()) {
+				return [
+					RuleErrorBuilder::message(
+						'Float used as array key, this emits deprecation notice.',
+					)->identifier('array.invalidOffset')->build(),
+				];
+			} elseif ($this->reportMaybes && $isFloat->maybe()) {
+				return [
+					RuleErrorBuilder::message(
+						'Float possibly used as array key, this emits deprecation notice.',
+					)->identifier('array.invalidOffset')->build(),
+				];
+			}
 		}
 
-		return [
-			RuleErrorBuilder::message(
-				sprintf('%s array key type %s.', $isSuperType->no() ? 'Invalid' : 'Possibly invalid', $dimensionType->describe(VerbosityLevel::typeOnly())),
-			)->identifier('offsetAccess.invalidOffset')->build(),
-		];
+		return [];
 	}
 
 }
diff --git a/src/Rules/Arrays/InvalidKeyInArrayItemRule.php b/src/Rules/Arrays/InvalidKeyInArrayItemRule.php
index 61c4fd342c..43f52cee22 100644
--- a/src/Rules/Arrays/InvalidKeyInArrayItemRule.php
+++ b/src/Rules/Arrays/InvalidKeyInArrayItemRule.php
@@ -4,6 +4,7 @@
 
 use PhpParser\Node;
 use PHPStan\Analyser\Scope;
+use PHPStan\Php\PhpVersion;
 use PHPStan\Rules\Rule;
 use PHPStan\Rules\RuleErrorBuilder;
 use PHPStan\Type\MixedType;
@@ -16,7 +17,10 @@
 class InvalidKeyInArrayItemRule implements Rule
 {
 
-	public function __construct(private bool $reportMaybes)
+	public function __construct(
+		private bool $reportMaybes,
+		private PhpVersion $phpVersion,
+	)
 	{
 	}
 
@@ -47,6 +51,24 @@ public function processNode(Node $node, Scope $scope): array
 			];
 		}
 
+		if ($this->phpVersion->getVersionId() >= 80100) {
+			$isFloat = $dimensionType->isFloat();
+
+			if ($isFloat->yes()) {
+				return [
+					RuleErrorBuilder::message(
+						'Float used as array key, this emits deprecation notice.',
+					)->identifier('array.invalidKey')->build(),
+				];
+			} elseif ($this->reportMaybes && $isFloat->maybe() && !$dimensionType instanceof MixedType) {
+				return [
+					RuleErrorBuilder::message(
+						'Float possibly used as array key, this emits deprecation notice.',
+					)->identifier('array.invalidKey')->build(),
+				];
+			}
+		}
+
 		return [];
 	}
 
diff --git a/tests/PHPStan/Rules/Arrays/InvalidKeyInArrayDimFetchRuleTest.php b/tests/PHPStan/Rules/Arrays/InvalidKeyInArrayDimFetchRuleTest.php
index 70c671135a..3cfba0f143 100644
--- a/tests/PHPStan/Rules/Arrays/InvalidKeyInArrayDimFetchRuleTest.php
+++ b/tests/PHPStan/Rules/Arrays/InvalidKeyInArrayDimFetchRuleTest.php
@@ -2,9 +2,12 @@
 
 namespace PHPStan\Rules\Arrays;
 
+use PHPStan\Php\PhpVersion;
 use PHPStan\Rules\Rule;
 use PHPStan\Rules\RuleLevelHelper;
 use PHPStan\Testing\RuleTestCase;
+use function array_filter;
+use function array_values;
 use const PHP_VERSION_ID;
 
 /**
@@ -16,12 +19,12 @@ class InvalidKeyInArrayDimFetchRuleTest extends RuleTestCase
 	protected function getRule(): Rule
 	{
 		$ruleLevelHelper = new RuleLevelHelper($this->createReflectionProvider(), true, false, true, false, false, true, false);
-		return new InvalidKeyInArrayDimFetchRule($ruleLevelHelper, true);
+		return new InvalidKeyInArrayDimFetchRule($ruleLevelHelper, true, new PhpVersion(PHP_VERSION_ID));
 	}
 
 	public function testInvalidKey(): void
 	{
-		$this->analyse([__DIR__ . '/data/invalid-key-array-dim-fetch.php'], [
+		$this->analyse([__DIR__ . '/data/invalid-key-array-dim-fetch.php'], array_values(array_filter([
 			[
 				'Invalid array key type DateTimeImmutable.',
 				7,
@@ -30,6 +33,12 @@ public function testInvalidKey(): void
 				'Invalid array key type array.',
 				8,
 			],
+			PHP_VERSION_ID >= 80100
+				? [
+					'Float used as array key, this emits deprecation notice.',
+					10,
+				]
+				: null,
 			[
 				'Possibly invalid array key type stdClass|string.',
 				24,
@@ -58,7 +67,13 @@ public function testInvalidKey(): void
 				'Invalid array key type DateTimeImmutable.',
 				48,
 			],
-		]);
+			PHP_VERSION_ID >= 80100
+				? [
+					'Float possibly used as array key, this emits deprecation notice.',
+					52,
+				]
+				: null,
+		])));
 	}
 
 	public function testBug6315(): void
diff --git a/tests/PHPStan/Rules/Arrays/InvalidKeyInArrayItemRuleTest.php b/tests/PHPStan/Rules/Arrays/InvalidKeyInArrayItemRuleTest.php
index 7a40122d1c..a38c2d587d 100644
--- a/tests/PHPStan/Rules/Arrays/InvalidKeyInArrayItemRuleTest.php
+++ b/tests/PHPStan/Rules/Arrays/InvalidKeyInArrayItemRuleTest.php
@@ -2,8 +2,11 @@
 
 namespace PHPStan\Rules\Arrays;
 
+use PHPStan\Php\PhpVersion;
 use PHPStan\Rules\Rule;
 use PHPStan\Testing\RuleTestCase;
+use function array_filter;
+use function array_values;
 use const PHP_VERSION_ID;
 
 /**
@@ -14,12 +17,12 @@ class InvalidKeyInArrayItemRuleTest extends RuleTestCase
 
 	protected function getRule(): Rule
 	{
-		return new InvalidKeyInArrayItemRule(true);
+		return new InvalidKeyInArrayItemRule(true, new PhpVersion(PHP_VERSION_ID));
 	}
 
 	public function testInvalidKey(): void
 	{
-		$this->analyse([__DIR__ . '/data/invalid-key-array-item.php'], [
+		$this->analyse([__DIR__ . '/data/invalid-key-array-item.php'], array_values(array_filter([
 			[
 				'Invalid array key type DateTimeImmutable.',
 				13,
@@ -32,7 +35,19 @@ public function testInvalidKey(): void
 				'Possibly invalid array key type stdClass|string.',
 				15,
 			],
-		]);
+			PHP_VERSION_ID >= 80100
+				? [
+					'Float used as array key, this emits deprecation notice.',
+					16,
+				]
+				: null,
+			PHP_VERSION_ID >= 80100
+				? [
+					'Float possibly used as array key, this emits deprecation notice.',
+					24,
+				]
+				: null,
+		])));
 	}
 
 	public function testInvalidKeyInList(): void
diff --git a/tests/PHPStan/Rules/Arrays/data/invalid-key-array-dim-fetch.php b/tests/PHPStan/Rules/Arrays/data/invalid-key-array-dim-fetch.php
index fb7514c6cb..d4b480d1e3 100644
--- a/tests/PHPStan/Rules/Arrays/data/invalid-key-array-dim-fetch.php
+++ b/tests/PHPStan/Rules/Arrays/data/invalid-key-array-dim-fetch.php
@@ -46,3 +46,8 @@
 $array[5][new \DateTimeImmutable()];
 $array[new \stdClass()][new \DateTimeImmutable()];
 $array[new \DateTimeImmutable()][] = 5;
+
+/** @var float|null $floatOrNull */
+$floatOrNull = null;
+$a[$floatOrNull];
+$a[$mixed];
diff --git a/tests/PHPStan/Rules/Arrays/data/invalid-key-array-item.php b/tests/PHPStan/Rules/Arrays/data/invalid-key-array-item.php
index cde86133df..0f97f7c052 100644
--- a/tests/PHPStan/Rules/Arrays/data/invalid-key-array-item.php
+++ b/tests/PHPStan/Rules/Arrays/data/invalid-key-array-item.php
@@ -13,4 +13,13 @@
 	new \DateTimeImmutable() => 'aaa',
 	[] => 'bbb',
 	$stringOrObject => 'aaa',
+	1.0 => 'aaa',
+	$mixed => 'aaa',
+];
+
+/** @var float|null $floatOrNull */
+$floatOrNull = null;
+
+$b = [
+	$floatOrNull => 'aaa',
 ];