Improve performance of Arr::dot method (#55495)

Author: cyppe

src/Illuminate/Collections/Arr.php

@@ -112,13 +112,19 @@ public static function dot($array, $prepend = '')
     {
         $results = [];
 
-        foreach ($array as $key => $value) {
-            if (is_array($value) && ! empty($value)) {
-                $results = array_merge($results, static::dot($value, $prepend.$key.'.'));
-            } else {
-                $results[$prepend.$key] = $value;
+        $flatten = function ($data, $prefix) use (&$results, &$flatten): void {
+            foreach ($data as $key => $value) {
+                $newKey = $prefix.$key;
+
+                if (is_array($value) && ! empty($value)) {
+                    $flatten($value, $newKey.'.');
+                } else {
+                    $results[$newKey] = $value;
+                }
             }
-        }
+        };
+
+        $flatten($array, $prepend);
 
         return $results;
     }