Add notice for `extension_dir`

docs/README.md

@@ -56,7 +56,7 @@ If you're experiencing any of the above, consider yourself damned. Ever since Xi
 ## ⚙️ How to use
 
 1. Download and install PHP 8.0+ for your system from the [official website](https://www.php.net/downloads).
-2. Enable OpenSSL and Curl extension in `php.ini`.
+2. Enable OpenSSL and Curl extension in `php.ini`. (And/or set `extension_dir` to your PHP's `ext` directory if script not work.)
 3. Place `adb.php` in [php-adb](https://github.com/MlgmXyysd/php-adb) to the directory.
 4. Download [platform-tools](https://developer.android.com/studio/releases/platform-tools) and place them in `libraries`. *Note: Mac OS needs to rename `adb` to `adb-darwin`.*
 5. Open a terminal and use PHP interpreter to execute the [script](../bypass.php).