How to observe events ?

Suppose we decide to send a mail after a process is over (progress meter reach 100%) and keep aware some users. We will see how to do this now.

First step is to declare a function (user callback) that will observe all progress meter events.

Interface of such function (callback) is pretty easy. It requires only one argument passed by reference ($notification) and that should contains a PEAR::Event_Dispatcher instance.

Here are, in purpose of our tutorial, a function that will observe events and send a mail, at end of process, to webmaster@site.com with a short message that gave time elapsed.

Second step is to attach this function (user callback) to the progress meter with the addListener() method.

<?php
require_once 'HTML/Progress2.php';
function getmicrotime($time)
{
list($usec, $sec) = explode(' ', $time);
return ((float)$usec + (float)$sec);
}
function myObserver(&$notification)
{
static $time_start;
$notifyName = $notification->getNotificationName();
$notifyInfo = $notification->getNotificationInfo();
switch ($notifyName) {
case 'onSubmit':
$time_start = getmicrotime($notifyInfo['time']);
break;
case 'onLoad':
$time_elapse = getmicrotime($notifyInfo['time']) - $time_start;
error_log ('process ID=5 is over (elapse time = '. $time_elapse . ' sec.)',
3, 'progress_observer.log');
break;
}
}
$pb = new HTML_Progress2();
$pb->setAnimSpeed(200);
$pb->setIncrement(10);
$pb->addListener('myObserver');
?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
"http://www.w3c.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en">
<head>
<title>Observer Pattern</title>
<?php
echo $pb->getStyle(false);
echo $pb->getScript(false);
?>
</head>
<body>
<?php
$pb->display();
$pb->run();
?>
</body>
</html>

Line 15 :

$notifyName contains event name triggered. Three issues : onSubmit, onLoad, onChange.

	Caution
	Event name is case sensitive: onsubmit does not match onSubmit.

Line 16 :

$notifyInfo contains array of additional informations.

For example :

Array
(
    [handler] => run
    [value] => 100
    [sender] => html_progress2
    [time] => 0.26838700 1127382686
)

Line 19 :

When progress meter start, it trigger a onSubmit event through the run() method. This event is catched into user callback and with help of additionnal info we compute and store start time.

Line 22 :

When progress meter reach 100%, it trigger a onLoad event through the run() method. This event is catched into user callback. We compute elapse time and send final result by mail to the webmaster of site.com

Lines 11-28, 33 :

All observers attached, are notified by each event. It's up to you to decide if you have to process an event or not. Here we will proceed only two events: onSubmit, onLoad.

Third step (optional) is stop listen events and then detach user function (callback) to the progress meter with the removeListener() method.

	Note
	While there are any observers attached, progress meter will continue to notify them of each event when they occured.

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Chapter 7. Listener	Home	Chapter 8. Quick Start with HTML_Progress2_Monitor

HTML_Progress2 : The Definitive Guide

How to observe events ?