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I Have been stuck for a couple of days now. I am attempting to call a simple python script from PHP. For the life of me I cannot figure out what the issue is. I have made the onoff.py script executable with chmod +x.

I can run the script just fine from the command line like this:

pi@raspberrypi:/var/www/html $ python onoff.py
LED on
LED off

My issue is when I try to call the script from PHP. I get nothing.

My Python Script:

#!/usr/bin/python
import RPi.GPIO as GPIO
import time
GPIO.setmode(GPIO.BCM)
GPIO.setwarnings(False)
GPIO.setup(18,GPIO.OUT)
print "LED on"
GPIO.output(18,GPIO.HIGH)
time.sleep(1)
print "LED off"
GPIO.output(18,GPIO.LOW)

My PHP Script:

<?php 
$command = escapeshellcmd('python /var/www/html/onoff.py');
$output = shell_exec($command);
echo $output;
?>

Any help is greatly appreciated!

EDIT:

if I change my onoff.py script to a simple while loop such as:

#!/usr/bin/python
x=1
while (x<10):
   print x
   x=x+1

the output on the browser is:

 1 2 3 4 5 6 7 8 9

I just don't understand why the loop will run but I get no output with the original python code.

EDIT 2:

Ok So I taking a different approach and trying to see where the code fails. I am adding bits of code at a time. Please see the following.

#!/usr/bin/python
import random
import time
import RPi.GPIO as GPIO

randomNumber = random.randint(1, 20)
GPIO.setmode(GPIO.BCM)
#GPIO.setup(18,GPIO.OUT)
print randomNumber

Now when I run the PHP it shows a random number so I know the python script is running. When I un-comment GPIO.setup(18,GPIO.OUT) and run the php I get a blank screen. I have no idea why this would make the script fail.

Caseyamn
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    Obligatory See also: [How can I debug exec() problems?](http://stackoverflow.com/q/12199353) – mario May 16 '16 at 00:16

2 Answers2

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shell_exec() will only return a string if $command a). Ran OK and assuming b). that it spits its response to STDOUT.

Use exec() and pass it your command, an integer $code and an empty array $response both of which are treated by PHP as arguments by reference.

Run your command thus:

$command = escapeshellcmd('/path/to/python /var/www/html/onoff.py');
$response = array();
$code = 0;
exec($command, $response, $code);
var_dump($code, $response);
die;

You should now see what is actually being given to PHP internally and why the Python script isn't working.

theruss
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  • Ok so I made the changes the output when I load the php page is: int(1) array(0) { } – Caseyamn May 16 '16 at 01:05
  • Hmmm sorry to say "it works for me" (Note I stripped it right down and removed escapeshellarg() as that's on;y really used if you have user input munged into a CLI command) #> php -a $cmd = '/usr/bin/python /path/to/test.py'; $code = 0; $res = []; exec($cmd, $res, $code); var_dump($code, $res); die; – theruss May 16 '16 at 03:00
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You need to use python before the script, i.e.:

$command = escapeshellcmd('python /var/www/html/onoff.py');

If it doesn't work, python probably ins't on the PATH of the apache user and you may need to use the full path to the python binary, use which to find the full path:

which python
//usr/bin/python

The use that value: 

$command = escapeshellcmd('/usr/bin/python /var/www/html/onoff.py');

Note:

  • Make sure apache user has execute permissions on onoff.py
Pedro Lobito
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