About Container, Command Bus, Event in Laravel5

About the bind method:
- These two bindings are the same. When $app->make(), both return a new instance

        $this->app->bind('App\DAO\UserDAO',function(){
        return new UserDAOImpl();
        });
        
        $this->app->bind('App\DAO\UserDAO','App\DAO\Impl\UserDAOImpl');

- bind can also be set alias, as follows, the first parameter is passed into the array, the key is the alias, and the value is the interface name
-

$this->app->bind(['dao.user' => 'App\DAO\UserDAO'],'App\DAO\Impl\UserDAOImpl');

- The third parameter is true, which means the effect of singleton is the same

$this->app->bind(['dao.user' => 'App\DAO\UserDAO'],'App\DAO\Impl\UserDAOImpl', true);

Command Bus
Essentially, it is a collection of calls to related methods
- Generate a Command

 php artisan make:command FirstCommand

At this time, a FirstCommand class will be generated under appCommands. The handle method is the specific execution content, and the handle method supports IoC.
- Call Command
Call the dispatch method in the Controller, as follows. The default Controller has `trait DispatchesCommands` so it has the dispatch method. When the following command is executed in the controller, the content in FirstCommand::handle() will be executed.

 $this->dispatch(new FirstCommand());

- Queue Command
Parameters will add
`IlluminateContractsQueueShouldBeQueued` interface and `SerializesModels` trait. This interface does not have any methods, just a marker (instanceof). - Pipeline command (TODO)
Event event
- Generate event class
Add the event name and the name of the Handler in the listen attribute in `EventServiceProvider`, for example:

    protected $listen = [
        'App\Events\FirstEvent' => [
            'App\Handlers\Events\FirstEventHandler',
        ],
    ];

Run command `php artisan event:generate`
will generate the corresponding file based on the content in $listen, and will not overwrite the already generated file.
- Processing events
Event registration is completed in the boot in `EventServiceProvider`. The handle method in Hanlder accepts a FirstEvent parameter, and handle is the processing method.
- Trigger event
-

 <span style="white-space:pre">	</span>\Event::fire(new FirstEvent()); 
        //or use the helper function
        event(new FirstEvent());

- Queue event
plus `IlluminateContractsQueueShouldBeQueued` tag, at the same time, use
`IlluminateQueueInteractsWithQueue` trait, Use methods such as

    $this->release(30);
    $this->delete(); 

when handling events Delete tasks, reset them, etc.
-
Subscriber
A subscriber is essentially a handler and must implement the subscribe($event) method.

    class ThirdEventHandler {
    
        /**
         * Create the event handler.
         *
         * @return void
         */
        public function __construct()
        {
            //
        }
    
        public function doSomething(){
            echo " ThirdEventHalder !!!..";
        }
    
        public function doSomethingToo(){
            echo "lalala, ThirdEventHalder again!!!..";
        }
    
        /**
         * 注册监听器给订阅者。
         *
         * @param  Illuminate\Events\Dispatcher  $events
         * @return array
         */
        public function subscribe($events)
        {
            $events->listen('App\Events\FirstEvent', 'App\Handlers\Events\ThirdEventHandler@doSomething');
    
            $events->listen('App\Events\FirstEvent', 'App\Handlers\Events\ThirdEventHandler@doSomethingToo');
        }
    
    }

How to subscribe?

    $subscriber = new App\Handlers\Events\ThirdEventHandler();
    Event::subscribe($subscriber);
    // or rely on IoC
    Event::subscribe('App\Handlers\Events\ThirdEventHandler');

Got it.
An Event can correspond to multiple Handlers, and the execution order of Handlers is consistent with the binding order.
A Subscriber can bind multiple events
The above introduces the Container, Command Bus, and Event in Laravel5, including the relevant content. I hope it will be helpful to friends who are interested in PHP tutorials.