[10.x] Fixes the Arr::dot() method to properly handle indexes array (#49507)

* Fixes the `Arr::dot()` method to properly handle arrays with integer keys

* Update tests/Support/SupportArrTest.php

Co-authored-by: Mior Muhammad Zaki <[email protected]>

---------

Co-authored-by: Mior Muhammad Zaki <[email protected]>

Author: kayw-geek

src/Illuminate/Collections/Arr.php

@@ -113,13 +113,13 @@ public static function dot($array, $prepend = '')
 
         foreach ($array as $key => $value) {
             if (is_array($value) && ! empty($value)) {
-                $results[] = static::dot($value, $prepend.$key.'.');
+                $results = array_merge($results, static::dot($value, $prepend.$key.'.'));
             } else {
-                $results[] = [$prepend.$key => $value];
+                $results[$prepend.$key] = $value;
             }
         }
 
-        return array_merge(...$results);
+        return $results;
     }
 
     /**

tests/Support/SupportArrTest.php

@@ -102,6 +102,12 @@ public function testDot()
         $array = Arr::dot(['foo' => ['bar' => 'baz']]);
         $this->assertSame(['foo.bar' => 'baz'], $array);
 
+        $array = Arr::dot([10 => 100]);
+        $this->assertSame([10 => 100], $array);
+
+        $array = Arr::dot(['foo' => [10 => 100]]);
+        $this->assertSame(['foo.10' => 100], $array);
+
         $array = Arr::dot([]);
         $this->assertSame([], $array);