When you setup a log in system, a session is being created by the log in script and it contains the logged user identity. This session and its value can be accessed by any other script by calling it (in your scripts).
The name of session storing logged in user identity depends on your security provider name. It’s name is:
securityProviderName + Id so if your security provider is called siteSecurity like here:
Then the session name will be: siteSecurityId
So, for example in your custom PHP script you’ll be referring to it like:
The same is valid for the other server models.