Adds a new observer to the dispatcher.

Observers are PHP callbacks. That means you may either pass a function name as a string or an array containing an object or class and a method to call.

The callback is used as a signature for the observer, which allows you to remove it by passing the exact same parameters to removeObserver().

Parameter

• mixed $callback

  Callback to notity, may either be a string containing the name of a global function or an array containing class or object and the name of the method to call.

• string $nName = EVENT_DISPATCHER_GLOBAL

  Acts as a filter: notify the observer only if the notification name matches the name passed in this parameter. Use EVENT_DISPATCHER_GLOBAL if the observer should be notified regardles of the notification name.

• string $class = ''

  Acts as a filter: notify the observer only if the sender of the notification matches the class passed in this parameter.

Return value

void

Note

This function can not be called statically.