EventSource

A PHP 5.3 library for creating an EventSource stream.

EventSource or Server-Sent-Events is a W3C specification that defines a protocol and an API for pushing data from the server to the client. This library is a server-side implementation of this protocol.

It is designed to be transport agnostic, allowing you to use it with apache directly or with other webservers, such as mongrel2.

Fetch

The recommended way to install EventSource is through composer.

Just create a composer.json file for your project:

{
    "require": {
        "igorw/event-source": "1.0.*"
    }
}

And run these two commands to install it:

$ curl -s http://getcomposer.org/installer | php
$ php composer.phar install

Now you can add the autoloader, and you will have access to the library:

<?php
require 'vendor/autoload.php';

Usage

The first thing you need to do is output the EventSource headers, so that the client knows it's talking to an EventSource server.

<?php

use Igorw\EventSource\Stream;

foreach (Stream::getHeaders() as $name => $value) {
    header("$name: $value");
}

After that you create a Stream which provides a nice API for creating events. Once you call flush, all queued events are sent to the client.

This example will send a new event every 2 seconds.

<?php

use Igorw\EventSource\Stream;

$stream = new Stream();

while (true) {
    $stream
        ->event()
            ->setData("Hello World")
        ->end()
        ->flush();
    
    sleep(2);
}

And an example JavaScript client:

var stream = new EventSource('stream.php');

stream.addEventListener('message', function (event) {
    console.log(event.data);
});

Advanced

Last event id

When your events have ids, the client will send a Last-Event-ID header on reconnection. You can read this value and re-send any events that occured after the one provided by the user.

<?php

$lastId = filter_input(INPUT_SERVER, 'HTTP_LAST_EVENT_ID');

if ($lastId) {
    $buffer = getMessagesAfter($lastId);

    foreach ($buffer as $message) {
        $stream->event()
            ->setId($message['id'])
            ->setData($message['data']);
    }

    $stream->flush();
}

Event namespacing

You can namespace events by using the setEvent method on the event. This allows you to bind to those event types specifically on the client side.

Here is a stream that sends two events. One of type foo and one of type bar.

<?php

$stream
    ->event()
        ->setEvent('foo')
        ->setData($message['data']);
    ->end()
    ->event()
        ->setEvent('bar')
        ->setData($message['data']);
    ->end()
    ->flush();

On the client you bind to that event instead of the generic message one. Do note that the message event will not catch these messages.

var stream = new EventSource('stream.php');

stream.addEventListener('foo', function (event) {
    console.log('Received event foo!');
});

stream.addEventListener('bar', function (event) {
    console.log('Received event bar!');
});

Sending JSON

In most applications you will want to send more complex data as opposed to simple strings. The recommended way of doing this is to use the JSON format. It can encode and decode nested structures quite well.

On the server side, simply use the json_encode function to encode a value:

<?php

$data = array('userIds' => array(21, 43, 127));

$stream
    ->event()
        ->setData(json_encode($data));
    ->end()
    ->flush();

On the client side, you can use JSON.parse to decode it. For old browsers, where JSON is not available, see json2.js.

var stream = new EventSource('stream.php');

stream.addEventListener('message', function (event) {
    var data = JSON.parse(event.data);
    console.log('User IDs: '+data.userIds.join(', '));
});

Custom handler

By default the library will assume you are running in a traditional apache-like environment. This means that output happens through echo. If you are using a server that handles web output in a different way (eg. app server), then you will want to change this.

A handler is simply a function that takes a chunk (a single event) and sends it to the client. You can define it as a lambda. Here is the default handler:

<?php

$handler = function ($chunk) {
    echo $chunk;
    ob_flush();
    flush();
};

You just pass it to the constructor of the stream:

<?php

$stream = new Stream($handler);

PHP time limit

In some setups it may be required to remove the time limit of the script. If you are having problems with your script dying after 30 or 60 seconds, add this line.

<?php
set_time_limit(0);

Polyfill

Most old browsers have not implemented EventSource yet. Luckily there is a polyfill available, that allows them to be used in a wider range of browsers.

Tests

$ phpunit

License

MIT, see LICENSE.