33     protected $emitter;  variable in OneCallBack
38         $this->emitter = new EventEmitter();
39         $this->emitter->on('foo', function() {
48             $this->emitter->emit('foo', []);
57     protected $emitter;  variable in ManyCallBacks
61         $this->emitter = new EventEmitter();
63             $this->emitter->on('foo', function() {
73             $this->emitter->emit('foo', []);
82     protected $emitter;  variable in ManyPrioritizedCallBacks
86         $this->emitter = new EventEmitter();
88             $this->emitter->on('foo', function() {
97             $this->emitter->emit('foo', []);