Overwrite existing value in .env when user entered a new value at the prompt

Dotenv.php

@@ -94,8 +94,12 @@ final class Dotenv {
       if (empty($value)) {
         $value = $default;
       }
+      $this->put($key, $value, TRUE);
     }
-    $this->put($key, $value);
+    else {
+      $this->put($key, $value);
+    }
+
     return $value;
   }