Web Things PHP

Implementation of an HTTP Web Thing. This library is compatible with PHP 7.1+.

Installation

The `webthingcan be installed usingcomposer` via the following command:

composer require webthing/webthing:^0.0.1

Running the Example

The following list of commands clones this repository and installs all dependencies using the composer and runs the single-thing.php example.

git clone https://github.com/maliknaik16/webthing-php.git
cd webthing-php
composer install
php examples/single-thing.php

Example Implementation

In this code-walkthrough we will set up a dimmable light and a humidity sensor (both using fake data, of course). Both working examples can be found in here.

Dimmable Light

Imagine you have a dimmable light that you want to expose via the web of things API. The light can be turned on/off and the brightness can be set from 0% to 100%. Besides the name, description, and type, a Light is required to expose two properties:

- `on`: the state of the light, whether it is turned on or off

- Setting this property via a ``PUT {"on": true/false}`` call to the REST API toggles the light.

- `brightness`: the brightness level of the light from 0-100%

- Setting this property via a PUT call to the REST API sets the brightness level of this light.

First we create a new Thing:

$light = new Thing(
  'urn:dev:ops:my-lamp-1234',
  'My Lamp',
  ['OnOffSwitch', 'Light'],
  'A web connected lamp'
);

Now we can add the required properties.

The `onproperty reports and sets the on/off state of the light. For this, we need to have aValue` object which holds the actual state and also a method to turn the light on/off. For our purposes, we just want to log the new state if the light is switched on/off.

$light->addProperty(new Property(
  $light,
  'on',
  new Value(TRUE, function($v) {
    echo "On-State is now " . $v . "\n";
  }),
  [
    '@type' => 'OnOffProperty',
    'title' => 'On/Off',
    'type' => 'boolean',
    'description' => 'Whether the lamp is turned on',
  ])
);

The `brightness` property reports the brightness level of the light and sets the level. Like before, instead of actually setting the level of a light, we just log the level.

$light->addProperty(new Property(
  $light,
  'brightness',
  new Value(50, function($v) {
    echo "Brightness is now " . $v . "\n";
  }),
  [
    '@type' => 'BrightnessProperty',
    'title' => 'Brightness',
    'type' => 'integer',
    'description' => 'The level of light from 0-100',
    'minimum' => 0,
    'maximum' => 100,
    'unit' => 'percent',
  ])
);

Now we can add our newly created thing to the server and start it:

// If adding more than one thing, use MultipleThings() with a name.
// In the single thing case, the thing's name will be broadcast.
$server = new WebThingServer(new SingleThing($thing), '127.0.0.1', 8888, 8081);

$server->start();
$server->startWebSocket();

This will start the server, making the light available via the WoT REST API and announcing it as a discoverable resource on your local network via mDNS.

Sensor

Let's now also connect a humidity sensor to the server we set up for our light.

A MultiLevelSensor (a sensor that returns a level instead of just on/off) has one required property (besides the name, type, and optional description): `level`. We want to monitor this property and get notified if the value changes.

First we create a new Thing:

$sensor = new Thing(
 'urn:dev:ops:my-humidity-sensor-1234',
  'My Humidity Sensor',
  ['MultiLevelSensor'],
  'A web connected humidity sensor'
);

Then we create and add the appropriate property:

- `level`: tells us what the sensor is actually reading

- Contrary to the light, the value cannot be set via an API call, as it wouldn't make much sense, to SET what a sensor is reading. Therefore, we are creating a readOnly property.

  ```php
  $level = new Value(0.0);
  $sensor->addProperty(new Property(
    $sensor,
    'level',
    $level,
    [
      '@type' => 'LevelProperty',
      'title' => 'Humidity',
      'type' => 'number',
      'description' => 'The current humidity in %',
      'minimum' => 0,
      'maximum' => 100,
      'unit' => 'percent',
      'readOnly' => TRUE,
    ])
  );
  ```

Now we have a sensor that constantly reports 0%. To make it usable, we need a thread or some kind of input when the sensor has a new reading available. For this purpose we start a thread that queries the physical sensor every few seconds. For our purposes, it just calls a fake method.

// $level is a `Value` object.
// $loop is a `React\EventLoop\Factory` object.
$loop->addPeriodicTimer(7, function() use ($level) {
  $new_level = readFromGpio();
  printf("Setting new humidity level: %s\n", $new_level);
  $level->notifyOfExternalUpdate($new_level);
});


function readFromGpio() {
  return abs(70.0 rand() (-0.5 + rand()));
}

This will update our `Valueobject with the sensor readings via the$level->notifyOfExternalUpdate(readFromGpio());call. TheValue` object now notifies the property and the thing that the value has changed, which in turn notifies all websocket listeners.

Resources

- https://iot.mozilla.org/wot - https://iot.mozilla.org/framework/ - https://iot.mozilla.org/gateway/ - https://www.w3.org/WoT/IG/

License

Mozilla Public License Version 2.0