native events in PHP

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

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