Change WePay::$all_scopes to WePay::getAllScopes()
Change WePay::$all_scopes to WePay::getAllScopes()

Having a public static variable means that one part of the application may inject anything into this variable and another part of the application will use it. Change it to a method and leave  the original variable deprecated (for backwards compatibility).
wepay/PHP-SDK,y2chaits/wepay-php-sdk,Firehed/PHP-SDK,skyzyx/wepay-php-sdk