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Date: Tue, 31 Aug 2004 07:53:04 +0200
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Cc: Alan Knowles <alan@akbkhome.com>
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Message-ID: <200408310753.05011.bf@ez.no>
Subject: Re: [PHP-DEV] native events in PHP
From: bf@ez.no (=?iso-8859-1?q?B=E5rd_Farstad?=)

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 =3D 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!
>         $this->onDebug[] =3D array($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 id=E8a to get into PHP in some way, however I =
would=20
recommend that the signal/slot technology used in QT should be considered.=
=20
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=20
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 =3D new MessageHandler();
$emailHandler =3D new MyEmailHandler();
$smsHandler =3D 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 id=E8a, but I think OO guys will like this.

=2D-b=E5rd