ronanguilloux/php-gpio

GPIO-related utils & toolkit PHP library

v1.0.0 2013-06-24 16:53 UTC

README

php-gpio is a simple PHP library to play with the Raspberry PI's GPIO pins.

It provides simple tools such as reading & writing to pins.

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Circuit snapshot

[UPDATE Fall 2014] Now compatible with both Raspberry Pi B Model & B+ Revision

Tl;dr

- "Hey, I just want to blink a LED from my raspberry pi hosted website!"
- "OK good guy: git clone https://github.com/ronanguilloux/php-gpio-web.git`
   & remember to come back here when you're lost ;-)"

=> php-gpio-web: a simple example for you to play with Leds & PHP

GPIO

General Purpose Input/Output (a.k.a. GPIO) is a generic pin on a chip whose behavior (including whether it is an input or output pin) can be controlled (programmed) through software. The Raspberry Pi allows peripherals and expansion boards (such as the Rpi Gertboard) to access the CPU by exposing the inputs and outputs.

For further informations about the Raspberry Pi's GPIO capabilities, see docs & schemas at http://elinux.org/RPi_Low-level_peripherals.

For Raspbeery Pi's GPIO controlling LEDs, have a look at a sample complete circuit diagram for a single LED, with detailled explanations & schemas, here.

For Raspbeery Pi's GPIO controlling sensors, check the DS18B20 (temperature sensor) in action here

Hardware prerequisites

After having installed & wired your LED & resistor on a breadboard, add appropriate modules from the Linux Kernel:

For LEDs, enable the gpio module :

$ sudo modprobe w1-gpio

(see a complete circuit diagram for a single LED + explanations & schemas here)

For sensors, enable the appropriate sensor. By example for a DS18B20 1-Wire digital temperature sensor:

$ sudo modprobe w1-therm

(see the DS18B20 in action on a Raspberry Pi here)

To load such kernel modules automatically at boot time, edit the /etc/modules file & add these two lines:

w1-gpio
w1-therm

Installation

The recommended way to install php-gpio is through composer.

Just run these three commands to install it

$ sudo apt-get install git
$ wget http://getcomposer.org/composer.phar
$ php composer.phar create-project --stability='dev' ronanguilloux/php-gpio intoYourPath

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

<?php

require 'vendor/autoload.php';

If you don't use neither Composer nor a ClassLoader in your application, just require the provided autoloader:

<?php

require_once 'src/autoload.php';

API Usage

The API usage requires sudo permissions.
To respect such permissions needs (say, for any web-related usage), see blinker file and the explanations below.

<?php

require 'vendor/autoload.php';

use PhpGpio\Gpio;

echo "Setting up pin 17\n";
$gpio = new GPIO();
$gpio->setup(17, "out");

echo "Turning on pin 17\n";
$gpio->output(17, 1);

echo "Sleeping!\n";
sleep(3);

echo "Turning off pin 17\n";
$gpio->output(17, 0);

echo "Unexporting all pins\n";
$gpio->unexportAll();

Understanding I/O permissions

Permissions make sense:

  • it's bad practice to run your webserver user (say, Apache2's www-data) as root
  • it's bad practice to chmod 777 /dev only because someone wants to blink a led freely

Such practices are regularly proposed on RPi forums, but they aren't security-aware & therefore not recommendable in an Internet environment. Instead, the good old /etc/sudoers file allow your linux users to execute single files with sudo permissions without password to type.

The blinker file solution ("one-file-to-blink-them-all")

In a PHP-based project, the API can only be used with sudo permissions. But there is a solution to avoid exposing your Raspbery Pi to security issues : Preparing & packaging inside an API client, in a single PHP file, the GPIO operation you need to run. In a hardware-based project, such operations are usualy few in number: blink a led, run a servomotor, etc. Such single PHP file containing your GPIO-related action can be called with determinated parameters from within your web-based application using exec() command :

(...)
$result = exec('sudo -t /usr/bin/php ./blinker 17 20000'); // calling the API client file
(...)

Such one-single PHP file to act as an API client for one GPIO action makes easier to configure specific sudo permissions in your /etc/sudoers file, as you'll see below. If you have more hardware operations to run (say, a LED + a servomotor + 2-3 sensors), more dedicated API client files, with their own parameters, is also very OK.

As an example of such solution, we provide a simple blinker php file, executable from the shell & from within your web based app. To run this blinker with sudo permissions but without password inputting, just allow your www-data or your pi user to run the blinker script using exec(). With the solution provided below, only one blinker script is needed to manage all your leds, and your webserver application needs only one php file to be specified in /etc/sudoers.

This is the regular linux-file-permission-system way to do such things, not a dummy chmod 777 bullshit.

Edit your /etc/sudoers file:

$ sudo visudo

Then add this two lines in your /etc/sudoers file :

    www-data ALL=NOPASSWD:/path/to/the/blinker

Replace /path/to/the/blinker with your single API client PHP file.

The blinker file provided now has the sufficient permissions & is ready to use the GPIO API. You do not need to install apache2-suexec nor suPHP.

You can test the blinker file solution with the blinkerTest.php file provided here:

<?php

# blinkTester.php

# Blinks the LED wired to the GPIO #17 pin with 0.2 second delay:
$result = exec('sudo -t /usr/bin/php ./blinker 17 20000');

Test your blinker:

$ php blinkTester.php

API Implementations

Some php-gpio api examples / demo :

  • Temperature-Pi: a simple php project reading & logging temperatures using a DS18B20 1-Wire digital temperature sensor & this php-gpio library.
  • Php-Gpio-Web: a website damn simple integration example of the php-gpio lib

Unit Tests

Running the full PhpUnit tests set over php-gpio requires a sudoable user, because of various gpio operations. Instead of installing phpunit, you can just download & use the single PhpUnit package. This can be easily done using cURL, to get the standalone PhpUnit's phar file:

$ wget http://pear.phpunit.de/get/phpunit.phar
$ chmod +x phpunit.phar
$ wget http://getcomposer.org/composer.phar
$ php composer.phar install --dev
$ sudo /usr/bin/php phpunit.phar

PHP Quality

For PHP quality fans, and for my self coding improvement, I wrote a little script available in the ./bin directory I launch to check my PHP code: It produces various stats & metrics & improvements tips on the code.

Credits

License

php-gpio is released under the MIT License.
See the bundled LICENSE file for details.
You can find a copy of this software here: https://github.com/ronanguilloux/php-gpio