Add three public functions:

- getStartDate
- getExpiryDate
- getUserLimit

Author: Sebastian Buckpesch

README.md

@@ -86,7 +86,7 @@ Attach one of these parameters to the url to modify the PHP SDK behaviour
 | getDevice()                      | Returns user device information                                                                                                                                                                                                                                         |                                                                                                       | array                                  |
 | getDeviceType()                  | Returns the device type of the current device mobile, tablet, desktop                                                                                                                                                                                                   |                                                                                                       | string                                 |
 | getEnvironment()                 | Returns if the app currently running on a website, facebook or direct website means the app is embedded via iframe to a website facebook means the app is embedded in a facebook page tab direct means the app is being accessed directly without iframe embed          |                                                                                                       | string                                 |
-| getExpirationDate()              | Returns a Datetime object, containing the date, the app license expires                                                                                                                                                                                                 |                                                                                                       | DateTime                               |
+| getExpiryDate()                  | Returns a Datetime object, containing the date, the app license expires                                                                                                                                                                                                 |                                                                                                       | DateTime                               |
 | getFacebook()                    | Returns all available Facebook information, like currently used fanpage and canvas information.                                                                                                                                                                         |                                                                                                       |                                        |
 | getLang()                        | Returns the currently used Language as Language Code (e.g. de_DE, en_US, ...)                                                                                                                                                                                           |                                                                                                       | string                                 |
 | getParams()                      | Returns all params submitted to the SmartLink before redirection                                                                                                                                                                                                        |                                                                                                       | array                                  |