A SiteAccess is a set of configuration settings that the application uses when you access the site through a specific address. When the user visits the site, the system analyzes the URI and compares it to rules specified in the configuration. If it finds a set of fitting rules, this SiteAccess is used.
Each SiteAccess can have different:
Many other settings in the application are also configured per SiteAccess (also known as "SiteAccess-aware").
When possible, always use semantic (SiteAccess-aware) configuration. Manually editing internal settings is possible, but at your own risk, as unexpected behavior can occur.
Use SiteAccess matchers to control which site is served when and to which user.
Make sure your custom development's configuration can be used with SiteAccesses.
Inject the SiteAccess service to get SiteAccess information in your custom PHP code.