Picture of Control an Arduino with PHP
Here's how to make your Arduino do things from over the internet without an ethernet or wifi shield. This is a simple way to make your project controllable from anywhere in the world!
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Step 1: Platform Compatability

This method WILL NOT work under Windows. I can't tell you how long it took me to figure that out. The command we're using, fopen() is not implemented the same way under Windows and Linux, so you have to use Linux. Never used it before? Don't panic, it's not that bad.

Step 2: Setting up your server

Picture of Setting up your server
You'll need to get a server running PHP for this to work. I'm going to assume you have a fresh copy of Ubuntu. There are literally thousands of tutorials on how to install Ubuntu, so I'll refer you to those if you don't. 

Open a terminal and type:
sudo apt-get install php5 mysql-server apache2

It will prompt you for a root MySQL password, so give it one.

Open a browser and go to http://localhost. You should see a page that says "It works!".  Next run this in a terminal:
sudo gedit /var/www/info.php

And paste in this code:

Save and close the file, then run
sudo service apache2 restart

Go to http://localhost/info.php
and you should see a purple table with a bunch of PHP stuff. If you do, congrats! You are now running a PHP server. Next, let's set up a page to control the Arduino.

Step 3: Touching the serial port in PHP

Picture of Touching the serial port in PHP
The core of this technique is the fopen() command. This is normally used for opening a document to edit within the code (like if you wrote a script to make a text file with some information in it and save it). Instead, we're going to exploit how linux views files and use it on a port. Install Arduino from the Ubuntu Software Manager. Plug in your Arduino and open the arduino window. You should see the device name under the ports menu. It will probably be /dev/ttyUSB0 or something similar. Here's some example code that will open that port as a file and write the numbers 1 to 6 based on what button is pressed:


$comPort = "/dev/ttyUSB0"; /*change to correct com port */

if (isset($_POST["rcmd"])) {
$rcmd = $_POST["rcmd"];
switch ($rcmd) {
     case Stop:
        $fp =fopen($comPort, "w");
  fwrite($fp, 1); /* this is the number that it will write */
     case Slow:
        $fp =fopen($comPort, "w");
  fwrite($fp, 2); /* this is the number that it will write */
  case Medium:
        $fp =fopen($comPort, "w");
  fwrite($fp, 3); /* this is the number that it will write */
  case Fast:
        $fp =fopen($comPort, "w");
  fwrite($fp, 4); /* this is the number that it will write */
case Right:
        $fp =fopen($comPort, "w");
  fwrite($fp, 5); /* this is the number that it will write */
case Left:
        $fp =fopen($comPort, "w");
  fwrite($fp, 6); /* this is the number that it will write */
  die('Crap, something went wrong. The page just puked.');


<center><h1>Arduino from PHP Example</h1><b>Version <?php echo $verz; ?></b></center>

<form method="post" action="<?php echo $PHP_SELF;?>">
<input type="submit" value="Left" name="rcmd">
<input type="submit" value="Right" name="rcmd"><br/>
<br />
<input type="submit" value="Stop" name="rcmd"><br/>
<br />
<input type="submit" value="Slow" name="rcmd">
<input type="submit" value="Medium" name="rcmd">
<input type="submit" value="Fast" name="rcmd">
<br />
<br />
<br />
<br />
<br />
<br />


Step 4: How it works & the Arduino side

Each time a button on the page is pressed, the case statement happens and the "file" (really the port) is opened, put into write mode, a single ASCII number is written, and then it's closed. You have to close it each time or else it won't work. On the Arduino side, simply read in from the serial port using Serial.read() in the loop(). I used a big if statement to check for each ASCII number, so if 1 is sent, then do one thing, if 2 is sent, do another thing, etc. Since you're running a PHP server, you can access the page on the server from anywhere in the world and it will control the Arduino. Here's some example arduino code I used to control some motors:

#include <Servo.h>

//First, set up the servos
Servo servo1;
Servo servo2;

int debugPin = 13; // used for an led to test stuff
int motor1Pin = 9; // the first motor's port number
int motor2Pin = 10; // the second motor's port number
int usbnumber = 0; //this variable holds what we are currently reading from serial

void setup() { //call this once at the beginning
    pinMode(motor1Pin, OUTPUT);
    pinMode(debugPin, OUTPUT);
    pinMode(motor2Pin, OUTPUT);
    Serial.begin(9600); //start up serial port

void loop() { //main loop
    if (Serial.available() > 0) { //if there is anything on the serial port, read it
        usbnumber = Serial.read(); //store it in the usbnumber variable

    if (usbnumber > 0) { //if we read something
        if (usbnumber == 49){
             servo2.write(93);//if we read a 1, stop
             analogWrite(debugPin, 0);
if (usbnumber == 50){
             servo2.write(120); //if we read a 2, slow
              analogWrite(debugPin, 85);
        if (usbnumber == 51){
             servo2.write(150); //if we read a 3, medium
            analogWrite(debugPin, 170);
        if (usbnumber == 52){
             servo2.write(179); //if we read a 4, fast
            analogWrite(debugPin, 255);
        if (usbnumber == 53){
             servo2.write(50); //if we read a 5, right
            analogWrite(debugPin, 255);
         if (usbnumber == 54){
             servo2.write(130); //if we read a 6, left
            analogWrite(debugPin, 255);
        usbnumber = 0; //reset
DavidR237 months ago

i get stack errors when I press any button

brianfit1 year ago

Nice one. Was looking for help in writing to the serial port from a php sequence to trigger output on the Arduino, this was just the ticket. No Servos, I just needed buttons and LED response. Thanks, aloishis89!

DavidR23 brianfit7 months ago

any luck?

wyatt.jameson9 months ago

Everytime you open the serial port with $fp =fopen($comPort, "w");, you have to sleep(2); in order to allow the arduino time to boot up. It's pretty annoying, because you have to wait 2 seconds every time you send a command, but unless you can sustain the connection, you have to do that.

jelimoore1 year ago

So I'd (like) to assume this also works under OSX, too?

SorinMS1 year ago

I've fixed the problem.

I give Apache permission to use the serial port. I did this in terminal
with the following command:

sudo adduser www-data dialout

Once this is done, I restart Apache with the following terminal command:

sudo /etc/init.d/apache2 restart

SorinMS1 year ago

It doesn't work for me.

hi, this only works for me if i have the arduino serial monitor open. if i close it and try then php just hangs. do you know why this might be?
for me /dev/tty.usbETC.. only worked when the arduino serial monitor was open, but if i used /dev/cu.usbETC... then it worked always (mac 10.8.4)

And even THAT isn't working with me, I'm on Mac as well.

Apparently when there is no serial connection happening, the arduino goes to sleep and takes a while to reboot. Go here http://playground.arduino.cc/Main/DisablingAutoRes... for some solutions. I just used the capacitor going to ground.

lkokoszka1 year ago

Do I have to allow PHP permissions to do anything special? I have been working over many a code and still nothing comes out of php other than ls and simple commands.

put this code-> $PHP_SELF="your file php name";

after this code


$comPort = "com4"; /*change to correct com port */



$comPort = "com4"; /*change to correct com port */


Thanks for your help. I forgot I inquired about this issue. I actually got my code to work after changing some permissions on the usb device (making the specific USB port world writable). Probably not the most secure thing to do, but will also be ignoring escape characters or what not.

dmanovski1 year ago
Put code file on running. Web server and access it from web browser
sss1 year ago
very good tutorials that help me to create web application controller
thanks so much

very good tutorials that help me to find what I need to build a web based application and control from internet sensors Using Arduino board
Raphango1 year ago
Congratulations! I really appreciate your idea! When my just bought arduino arrives i'll try it!
ajindam2 years ago
For windows users, this code should do.

exec("mode COM3: BAUD=9600 PARITY=n DATA=8 STOP=1 to=off dtr=off rts=off");
$fp = fopen("COM3", "w");
fwrite($fp, "1"); //write string to serial
Thank you so much for posting this! I've been searching for a way to control a parallax propeller from a wamp server. This code got me up and running.
abubakr0221 year ago
where we have to put this code?