diff --git a/CLAUDE.md b/CLAUDE.md
index d9695a8..193e024 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -6,7 +6,7 @@ This file provides guidance to Claude Code (claude.ai/code) when working with co
 
 `bitapps/wp-validator` — a Composer library (PSR-4: `BitApps\WPValidator\` → [src/](src/)) providing Laravel-style validation and sanitization for WordPress. Public API and the full rule list are documented in [README.md](README.md); update it when adding a rule or sanitizer.
 
-**PHP 7.2 is the floor.** No typed properties, no arrow functions, no null coalescing assignment, no union types. Return types on methods are used and fine. [rector.php](rector.php) pins `PhpVersion::PHP_72` and skips the typed-property rectors for this reason.
+**PHP 7.4 is the floor.** No union types or other PHP 8+ syntax. Return types on methods are used and fine. [rector.php](rector.php) pins `PhpVersion::PHP_74` and skips the typed-property rectors.
 
 ## Commands
 
@@ -14,7 +14,7 @@ This file provides guidance to Claude Code (claude.ai/code) when working with co
 composer test:unit                                  # full suite (Pest, --testdox, excludes group 'db')
 ./vendor/bin/pest tests/Rules/BetweenTest.php       # single file
 ./vendor/bin/pest --filter='between accepts a length of zero'   # single test by name
-composer compat                                     # PHPCompatibility check against PHP 7.2
+composer compat                                     # PHPCompatibility check against PHP 7.4
 composer rector                                     # Rector dry-run (never auto-applies)
 ```
 
diff --git a/composer.json b/composer.json
index 251ed5c..7956bd3 100644
--- a/composer.json
+++ b/composer.json
@@ -32,7 +32,7 @@
     },
 
     "require": {
-        "php": ">=7.2"
+        "php": ">=7.4"
       },
     "require-dev": {
         "pestphp/pest": "^2.18",
diff --git a/rector.php b/rector.php
index f815ed8..a808ff6 100644
--- a/rector.php
+++ b/rector.php
@@ -13,7 +13,7 @@
     ->withPaths([
         __DIR__ . '/src',
     ])
-    ->withPhpVersion(PhpVersion::PHP_72)
+    ->withPhpVersion(PhpVersion::PHP_74)
     ->withSkip([
         UnwrapFutureCompatibleIfPhpVersionRector::class,
         TypedPropertyFromStrictConstructorRector::class,
@@ -29,4 +29,4 @@
         // strictBooleans: true,
         // naming: true,
     )
-    ->withSets([SetList::PHP_72]);
+    ->withSets([SetList::PHP_74]);
diff --git a/src/InputDataContainer.php b/src/InputDataContainer.php
index 71d2b5c..1126e9c 100644
--- a/src/InputDataContainer.php
+++ b/src/InputDataContainer.php
@@ -7,7 +7,7 @@ class InputDataContainer
 
     private $data = [];
 
-    private $attributeKey;
+    private $attributeKey = '';
 
     private $attributeLabel;
 
@@ -18,7 +18,7 @@ public function __construct($data = [])
 
     public function setAttributeKey($key): void
     {
-        $this->attributeKey = $key;
+        $this->attributeKey = $key ?? '';
     }
 
     public function getAttributeKey()
@@ -28,22 +28,17 @@ public function getAttributeKey()
 
     public function getAttributeValue($key = null)
     {
-        $keys = explode('.', trim($this->attributeKey ?? '', '[]'));
-
-        $data = $this->data;
+        $keys = explode('.', trim($this->attributeKey, '[]'));
 
         if (count($keys) > 1) {
-            $data = $this->getValueFromPath($keys, $data);
-        } elseif ($key && isset($data[$key])) {
-            return $data[$key];
-        } elseif (isset($data[$this->attributeKey])) {
-            return $data[$this->attributeKey];
-        } else {
-            return null;
+            return $this->getValueFromPath($keys, $this->data);
         }
 
-        return $data;
+        if ($key !== null && isset($this->data[$key])) {
+            return $this->data[$key];
+        }
 
+        return $this->data[$this->attributeKey] ?? null;
     }
 
     public function setAttributeLabel($value): void
@@ -63,7 +58,7 @@ public function getData()
 
     public function setAttributeValue($value): void
     {
-        $keys = explode('.', trim($this->attributeKey ?? '', '[]'));
+        $keys = explode('.', trim($this->attributeKey, '[]'));
 
         if (\count($keys) > 1) {
             $this->setNestedElement($this->data, $keys, $value);
diff --git a/tests/InputDataContainerTest.php b/tests/InputDataContainerTest.php
new file mode 100644
index 0000000..7cf3534
--- /dev/null
+++ b/tests/InputDataContainerTest.php
@@ -0,0 +1,104 @@
+<?php
+
+use BitApps\WPValidator\InputDataContainer;
+use BitApps\WPValidator\Rules\PresentRule;
+use BitApps\WPValidator\Validator;
+
+function collectDeprecations(callable $callback): array
+{
+    $deprecations = [];
+
+    set_error_handler(function ($level, $message) use (&$deprecations) {
+        $deprecations[] = $message;
+
+        return true;
+    }, E_DEPRECATED);
+
+    try {
+        $callback();
+    } finally {
+        restore_error_handler();
+    }
+
+    return $deprecations;
+}
+
+test('getAttributeValue without a key does not use null as an array offset', function () {
+    $container = new InputDataContainer(['name' => 'John']);
+    $container->setAttributeKey('name');
+
+    $deprecations = collectDeprecations(function () use ($container) {
+        $container->getAttributeValue();
+    });
+
+    expect($deprecations)->toBe([]);
+    expect($container->getAttributeValue())->toBe('John');
+});
+
+test('getAttributeValue before an attribute key is set does not use null as an array offset', function () {
+    $container = new InputDataContainer(['name' => 'John']);
+
+    $deprecations = collectDeprecations(function () use ($container) {
+        $container->getAttributeValue();
+    });
+
+    expect($deprecations)->toBe([]);
+    expect($container->getAttributeValue())->toBeNull();
+});
+
+test('setAttributeValue before an attribute key is set does not use null as an array offset', function () {
+    $container = new InputDataContainer(['name' => 'John']);
+
+    $deprecations = collectDeprecations(function () use ($container) {
+        $container->setAttributeValue('Doe');
+    });
+
+    expect($deprecations)->toBe([]);
+    expect($container->getData())->toBe(['name' => 'John', '' => 'Doe']);
+    expect($container->getAttributeValue())->toBe('Doe');
+});
+
+test('a null attribute key does not use null as an array offset', function () {
+    $container = new InputDataContainer(['name' => 'John']);
+    $container->setAttributeKey(null);
+
+    $deprecations = collectDeprecations(function () use ($container) {
+        $container->getAttributeValue();
+        $container->setAttributeValue('Doe');
+    });
+
+    expect($deprecations)->toBe([]);
+});
+
+test('present rule before an attribute key is set does not use null as an array offset', function () {
+    $rule = new PresentRule();
+    $rule->setInputDataContainer(new InputDataContainer(['name' => 'John']));
+
+    $deprecations = collectDeprecations(function () use ($rule) {
+        $rule->validate('John');
+    });
+
+    expect($deprecations)->toBe([]);
+});
+
+test('getAttributeValue does not read an empty string key when called without a key', function () {
+    $container = new InputDataContainer(['' => 'wrong', 'name' => 'John']);
+    $container->setAttributeKey('name');
+
+    expect($container->getAttributeValue())->toBe('John');
+});
+
+test('getAttributeValue reads falsy explicit keys', function () {
+    $container = new InputDataContainer(['first', 'second']);
+    $container->setAttributeKey(1);
+
+    expect($container->getAttributeValue(0))->toBe('first');
+    expect($container->getAttributeValue('0'))->toBe('first');
+});
+
+test('same rule compares against a field named 0', function () {
+    $validator = new Validator();
+
+    expect($validator->make(['0' => 'secret', 'confirm' => 'wrong'], ['confirm' => ['same:0']])->fails())->toBeTrue();
+    expect($validator->make(['0' => 'secret', 'confirm' => 'secret'], ['confirm' => ['same:0']])->fails())->toBeFalse();
+});