phpf/event

Phpf Event package

Event

Simple, powerful, and extendable JavaScript-like events for PHP., _(*1)

1. Features
2. Basic Usage
3. Examples
   • Priorities
   • Cancelling Events
   • Single-Listener Events
   • Returning Results
   • Stopping Propagation
   • Retrieving Completed Events
   • Custom Event Objects

Features

• Simple syntax (on() to bind, trigger() to emit)
• Extendable event objects
• Priority ordering of callbacks
• Callbacks can be any callable (not limited to closures)
• An arbitrary number of arguments can be passed to callbacks
• Prevent default behavior (preventDefault()), or stop propagation altogether (stopPropagation())
• One-time events (one())
• Event cancelling (off())

Basic Usage

$events = new \Phpf\Event\Manager;

$events->on('myevent', function ($event, $myarg) {

    if ($event->isDefaultPrevented()){
        return;
    }

    echo "I'm doing my event called $myarg!";
});

$events->trigger('myevent', 'Example'); // outputs "I'm doing my event called Example!"

Examples

Priorities

By default, events are added with a priority of 10 and executed from lowest to highest:, _(*2)

$events->on('myevent', function ($event) { echo "Child"; }, 15);

$events->on('myevent', function ($event) { echo "Bear"; }, 9);

$events->trigger('myevent'); // outputs "BearChild"

You can change the sort order to high-to-low like so:, _(*3)

$events->setSortOrder(\Phpf\Event\Manager::SORT_HIGH_LOW);

Cancelling Events

To cancel an event, simply call the off() method:, _(*4)

$events->off('myevent');

This will remove any listeners bound to the event, so they will not be called if subsequently triggered., _(*5)

Single-Listener Events

You can limit an event's execution to a single listener by using the one() method instead of on():, _(*6)

$events->one('myevent', function ($event) {
    echo "I will print.";
});

$events->on('myevent', function ($event) {
    echo "I will not print, even though I was bound later.";
});

$events->trigger('myevent'); // Prints "I will print."

Returning Results

When events listeners are executed, any value returned from the listener will be collected; on completion (or propagation stoppage), the results will be returned as an indexed array., _(*7)

For example:, _(*8)

$events->on('myevent', function ($event) {

    return 'Hello';
});

$events->on('myevent', function ($event) {

    return 'Goodbye';
});

$results = $events->trigger('myevent');

print_r($results); // array(0 => 'Hello', 1 => 'Goodbye');

Stopping Propagation

Like JS, propagation of events can be stopped by a listener at any time., _(*9)

$events->on('myevent', function ($event) {

    echo "This will be printed";

    $event->stopPropagation();
});

$events->on('myevent', function ($event) {

    echo "This will not be printed.";
});

$events->on('myevent', function ($event) {

    echo "I will not be called.";
}, 12);

$events->on('myevent', function ($event) {

    echo "I will print second.";

    $event->stopPropagation();
}, 11);

$events->on('myevent', function ($event) {

    echo "I will print first.";
});

Retrieving Completed Events

The completed events and their returned arrays are stored for later use. The event object can be retrieved using the event() method, the results using the result() method:, _(*10)

$results = $events->trigger('myevent');

// ...later on, in another script:
$myevent = $events->event('myevent');
$sameResults = $events->result('myevent');

// ... do stuff with event/results

// re-trigger the event !
$newResults = $events->trigger($myevent);

Custom Event Objects

You can also pass an instance of the Event class to the trigger() method instead of the event ID. This way, you can use custom event objects., _(*11)

For example, if you want listeners to be able to modify a single returned value (a "filter"), you could create a class like this:, _(*12)

namespace MyEvents;

use Phpf\Event\Event;

class FilterEvent extends Event {

    protected $value;

    public function __construct($id, $initial_value) {
        // must call parent constructor with id if overriding
        parent::__construct($id);
        $this->value = $initial_value;
    }

    public function getValue() {
        return $this->value;
    }

    public function setValue($value) {
        $this->value = $value;
    }
}

And then use it like so:, _(*13)

$events->on('myFilterEvent', function ($event) {
    $newval = rtrim($event->getValue(), 's') . ' objects';
    $event->setValue($newval);
});

$events->on('myFilterEvent', function ($event) {
    $event->setValue($event->getValue() . ' are cool.');
});

// Create new object with initial value "Custom events"
$filterEvent = new \MyEvents\FilterEvent('myFilterEvent', 'Custom events');

$events->trigger($filterEvent);

$filtered = $events->event('myFilterEvent');

echo $filtered->getValue(); // Prints "Custom event objects are cool."