PHP site to control Arduino sends code on load of webpage

Question

I am trying to create a domotica setup with my Arduino and my server. Before using the RF transmitter, I'm trying to control LEDs (setting them on/off) from my php webpage.

It all works perfectly, except for the fact that LED1 turns on when I'm loading/refreshing the webpage. My webpage contains the following code (which I adapted from https://www.lassiemarlowe.com/tutorials/power-led-bulbs-arduino-php-part-2/):

<html>
<head>
<title>Arduino Domotica Control Panel</title>

Some css code here...

<?php
switch($_POST)
{
    case isset($_POST['submitOn']):
        $fp = fopen("/dev/ttyUSB1", "w");
        fwrite($fp, 1);
        fclose($fp);
        break;
    case isset($_POST['submitOff']):
        $fp = fopen("/dev/ttyUSB1", "w");
        fwrite($fp, 2);
        fclose($fp);
        break;
    case isset($_POST['submitOn1']):
        $fp = fopen("/dev/ttyUSB1", "w");
        fwrite($fp, 3);
        fclose($fp);
        break;
    case isset($_POST['submitOff1']):
        $fp = fopen("/dev/ttyUSB1", "w");
        fwrite($fp, 4);
        fclose($fp);
        break;
    case isset($_POST['submitOn2']):
        $fp = fopen("/dev/ttyUSB1", "w");
        fwrite($fp, 5);
        fclose($fp);
        break;
    case isset($_POST['submitOff2']):
        $fp = fopen("/dev/ttyUSB1", "w");
        fwrite($fp, 6);
        fclose($fp);
        break;
    case isset($_POST['allon']):
        $fp = fopen("/dev/ttyUSB1", "w");
        fwrite($fp, 7);
        fclose($fp);
        break;
    case isset($_POST['alloff']):
        $fp = fopen("/dev/ttyUSB1", "w");
        fwrite($fp, 8);
        fclose($fp);
        break;
}

?>
</head>


<body>

<h1>Control Panel</h1>


<form class="control-panel-frm" method="post" action="<?php echo htmlspecialchars($_SERVER["PHP_SELF"]);?>">
    <input type='submit'  class="s3d turnOn" name='submitOn' value='LED 1 on'>
    <input type='submit' class="s3d switchoff" name='submitOff' value='LED 1 off'>
    <br><br>
    <input type='submit'  class="s3d turnOn" name='submitOn1'  value='LED 2 on'>
    <input type='submit'  class="s3d switchoff"  name='submitOff1' value='LED 2 off'>
    <br><br>
    <input type='submit'  class="s3d turnOn" name='submitOn2'  value='LED 3 on'>
    <input type='submit'  class="s3d switchoff"  name='submitOff2'  value='LED 3 off'>
    <br><br>
    <input type='submit' class="s3d turnOn"  name='allon' value='All LEDs on'>
    <input type='submit'  class="s3d switchoff"  name='alloff' value='All LEDs off'>

</form>

As stated before, the problem is that LED1 (corresponding to php post 'submitOn') turns on when I load/refresh the webpage. When checking the serial monitor, the Arduino receives a '1'.

What should I change in order to prevent my webpage from sending anything to the Arduino when it loads?

pmayer · Accepted Answer · 2017-09-25T15:36:53.103

I think you understood switch wrong. Switch compares the value from the braces () with the value given by case. See the manual page for switch to get more clarification on this.

Besides that you did not unterstood the transfer of data from a html form to a PHP application. You send LED 1 on as value for the form element submitOn.

Try this:

<?php
$actions = [
    'submitOn' => 1,
    'submitOff' => 2, 
    //...
];

if(!empty($_POST['action']) && array_key_exists($_POST['action'], $actions)){
    $fp = fopen("/dev/ttyUSB1", "w");
    fwrite($fp, $actions[$_POST['action']]);
    fclose($fp);
}

?>
<form class="control-panel-frm" method="post" action="">
    <input type="submit" class="s3d turnOn" name="action" value="submitOn">
    <input type="submit" class="s3d switchoff" name="action" value="submitOff">
</form>

Note that an empty action of a form sends the form data to the current page. See Two submit buttons in one form for the use of more than one submit button.

There is one syntax error in the `if` line of the code; the line should be ended by 3 brackets `)` instead of the two as seen in the code. — DaanMusic, Nov 09 '15 at 10:12

PHP site to control Arduino sends code on load of webpage

1 Answers1