fix casing issue with guarded

Author: taylorotwell

src/Illuminate/Database/Eloquent/Concerns/GuardsAttributes.php

@@ -163,7 +163,7 @@ public function isFillable($key)
      */
     public function isGuarded($key)
     {
-        return in_array($key, $this->getGuarded()) || $this->getGuarded() == ['*'];
+        return $this->getGuarded() == ['*'] || ! empty(preg_grep('/^'.preg_quote($key).'$/i', $this->getGuarded()));
     }
 
     /**

tests/Integration/Database/EloquentModelTest.php

@@ -29,6 +29,15 @@ protected function setUp(): void
         });
     }
 
+    public function testCantUpdateGuardedAttributesUsingDifferentCasing()
+    {
+        $model = new TestModel2;
+
+        $model->fill(['ID' => 123]);
+
+        $this->assertNull($model->ID);
+    }
+
     public function testUserCanUpdateNullableDate()
     {
         $user = TestModel1::create([