我正在设置Paypal Pro，并考虑安全地存储我的密码。这是Paypal的测试代码和注释。为了安全地保护密码，我应该如何更改此代码？
我只在这里存储一个密码 - 我们的API密码。
/**
# API_password: The password associated with the API user
# If you are using your own API username, enter the API password that
# was generated by PayPal below
# IMPORTANT - HAVING YOUR API PASSWORD INCLUDED IN THE MANNER IS NOT
# SECURE, AND ITS ONLY BEING SHOWN THIS WAY FOR TESTING PURPOSES
*/
define('API_PASSWORD', 'LJKL235JL532K35');