An event dispatcher in a tweet

Dispatch1.php

<?php

// Version 1

// Minified
// class Dispatch{function add($e,$l){$this->l[$e][]=$l;}function trigger($e,$d){foreach ($this->l[$e] as $l)call_user_func_array($l, $d);}}

class Dispatch{
    function add($e, $l) {
        $this->l[$e][] = $l;
    }

    function trigger($e, $d) {
        foreach ($this->l[$e] as $l) {
            call_user_func_array($l, $d);
        }
    }
}


class Greeter {
    public function greet($name) {
        echo "Hello $name\n";
    }
} 

$dispatch = new Dispatch();
$dispatch->add('greet', array(new Greeter, 'greet'));

$dispatch->trigger('greet', array('Bob'));

Dispatch2.php

<?php

// Version 2

// Minified
// class Dispatch{function add($e,$l){$this->l[$e][]=$l;}function trigger($e,$d){foreach($this->l[$e] as$l)$l($d);}}

class Dispatch {
 function add($e, $l) { $this->l[$e][]=$l; }
 function trigger($e, $d) { foreach ($this->l[$e] as $l) $l($d); }
}


$dispatch = new Dispatch();
$dispatch->add('greet', function ($name) {
    echo "Hello $name\n";
});

$dispatch->trigger('greet', 'Bob');

Nicked your update @mathiasverraes and used all that saved space you made to add event propagation control.

✔︎ It calls event listeners in the right order with event propagation

<?php

function e($n,$p,$c=0){static $a;@krsort($a[$n]);if($c)$a[$n][$p][]=$c;else foreach($a[$n] as$q)foreach($q as$r)if(!$r($p))return;}

function it($m,$p){echo ($p?'✔︎':'✘')." It $m\n"; if(!$p){$GLOBALS['f']=1;}}function done(){if(@$GLOBALS['f'])die(1);}

ob_start();
e(
    'event',
    0,
    function ($data) {
        echo "event, $data, priority 0;";
        return true;
    }
);
e(
    'event',
    10,
    function ($data) {
        echo "event, $data, priority 10;";
        return true;
    }
);
e(
    'other_event',
    -5,
    // Should not reach this event due to propagation termination
    function ($data) {
        echo "other_event, $data, priority -5;";
        return true;
    }
);
e(
    'other_event',
    5,
    function ($data) {
        echo "other_event, $data priority 5;";
        return false; // Will stop event propagation after this event
    }
);
e('event', 'dataX');
e('other_event', 'dataY');
$output = ob_get_contents();
ob_end_clean();

it(
    'calls event listeners in the right order with event propagation',
    $output === 'event, dataX, priority 10;event, dataX, priority 0;other_event, dataY priority 5;'
);

maybe you are interested on a something like a framework ... https://github.com/liuggio/sized140

Dependency injection container in a tweet ... https://gist.github.com/jm42/3c32dd50bb9d09f57c4a