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Date: Wed, 01 Sep 2004 01:59:06 +0800
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To: Al Baker <ajb732@comcast.net>
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Subject: Re: [PHP-DEV] native events in PHP
From: alan@akbkhome.com (Alan Knowles)

Actually, php-gtk has it's own connect/emit mechanism, what is 
problematic, is that a number of projects (both pear packages and 
others) utilize a callback/event model, and the only 2 ways to implement 
it are as a visitor type class, or recode the same simple method in a 
number of places.

In DBDO (my latest phpextension experiment), I wanted to be able to 
register callback handlers for debug logging, and it would have been 
nice to use an existing set of tools/API to deal with it. (in the end I 
copied code from the php-gtk extension)

Regards
Alan

Al Baker wrote:

>There's nothing stopping someone from writing their own classes for
>dispatching and handling events and implementing callbacks today...
>
>Are you suggesting something built into PHP like the Java system event
>queue that people can define their own dispatchers and handlers for?
>The QT example below is similar, connecting signals to slots instead of
>dispatching events to listeners.
>
>I guess it makes sense for long running scripts, like PHP-GTK. You
>probably also want all those events processed in order by the same
>system component (i.e. the system event queue). However, most web
>applications have only one "event stimulus" at a time, i.e. the request
>coming in from the web server.  They are then processed and go away in a
>blink of an eye.
>
>Hey, for PHP-GTK probably want to take it a step further and have some
>standard event classes (WindowEvent, FocusEvent, etc).  Do these already
>exist? -- haven't looked at PHP-GTK in much detail.
>
>Al
>
>On Tue, 2004-08-31 at 07:53 +0200, Bård Farstad wrote:
>  
>
>>On Tuesday 31 August 2004 05:46, Alan Knowles wrote:
>>    
>>
>>>I've been looking at events in PHP, at present, in PEAR, there are lots
>>>of different methods to add callbacks, to packages, for various
>>>purposes. It seriously lacks cohesion, and would be nice to sort out at
>>>the language level.
>>>
>>>Having seen C#, while not perfect, it is an interesting model.
>>>There's a very short note on C#, and an idea for a PHP syntax.
>>>http://www.akbkhome.com/wiki.php/DBDO/signals.html
>>>
>>>It suggests:
>>>
>>>class xxxx {
>>>      // event registers a method, that hooks into the generic event
>>>handler.
>>>      public event $onDebug = array();
>>>
>>>
>>>      function somemethod() {
>>>
>>>        // add a handler to an event..
>>>    // this is the natrual syntax for this, but does open the door to
>>>someone wiping the stack!
>>>        $this->onDebug[] = array($this,'mycallback');
>>>
>>>
>>>    // initiate the signals. (function name matches the var!)
>>>    $this->onDebug($x,$y);
>>>     }
>>>     // a handler..
>>>     function mycallback($x,$y) {
>>>    echo "debug hander got $x , $y\n";
>>>     }
>>>}
>>>
>>>
>>>Anyone care to comment on
>>>a) the feasibility
>>>b) the "should it be implemented" question.
>>>c) the "any better ideas" question...
>>>      
>>>
>>I think this would be a good idèa to get into PHP in some way, however I would 
>>recommend that the signal/slot technology used in QT should be considered. 
>>It's really simple and flexible to use.
>>
>>Here is an example of how this could be done in PHP (not the best example, but 
>>it should show how it works ):
>>
>>class MessageHandler
>>{
>>    public signal messageSent( $message );
>>
>>    private function checkQueue()
>>    {
>>        foreach ( $messageQueue as $messsage )
>>        {
>>            // Send a signal for each message
>>            // So that the connected slots can handle it
>>            emit messageSent( $message );
>>        }
>>    }
>>}
>>
>>class MyEmailMessageHandler
>>{
>>   public slot sendEmail( $message )
>>   {
>>        mail( $message );
>>   }
>>}
>>
>>class MySMSMessageHandler
>>{
>>   public slots sendSMS( $message )
>>   {
>>       sendSMS( $message );
>>   }
>>}
>>
>>When you instantiate your objects:
>>
>>$messageHandler = new MessageHandler();
>>$emailHandler = new MyEmailHandler();
>>$smsHandler = new MySMSHandler();
>>
>>// Connect is used to connect signals with slots.
>>// A signal can be used by multiple slots and a slot
>>// can have multiple signals connected to it.
>>connect( $messageHandler, 'messageSent', $emailHandler, 'sendEmail' );
>>connect( $messageHandler, 'messageSent', $emailHandler, 'sendSMS' );
>>
>>There is some documentation on how that system works here:
>>http://doc.trolltech.com/3.3/signalsandslots.html
>>
>>It's just an idèa, but I think OO guys will like this.
>>
>>--bård
>>
>>    
>>
>
>  
>