Accessing shell script on remote server - php

Question

So first of all I have 2 Servers:
Raspberry pi
Linux Debian server
The pi has a script that displays the current Temperature in a room.
This is the script :
#!/bin/bash
i2cset -y 1 0x48 0xEE
dte=$(date +%Y-%m-%d)
tme=$(date +%H:%M:%S)
hexraw=$(i2cget -y 1 0x48 0xAA w)
msb=$(echo ${hexraw:4:2})
lsb=$(echo ${hexraw:2:1})
dec=$(printf "%d\n" "0x$msb$lsb")
temp=$(echo "scale=1; $dec/16" | bc)
echo $temp
exit
Displaying the temperature on the pi's website works fine.
But then I have another script on the linux server that takes the value of the pi's script:
#!/bin/bash
x=$(ssh pi#172.16.248.210 sudo /home/pi/CurrTemp;)
echo $x
This works too. But when I want to display the Temp on my Linux server website(with shell_exec()) it doesn't work. The var_dump is empty.
PHP:
I've tried to write it with a "sudo".
I've changed the script owner to root.

Answer 1

ssh authentication does not work since the web server can't (and should) access your ssh keys.
You have to options (where the latter is definitely preferred!):
Create another ssh key for the web server on the Debian server and add to allowed_keys on the PI. You may restrict the key to allow only that command.
Create a little web service on the PI and output the temperature in plain text, xml, json or whatever. The use file_get_contents() to obtain the file over HTTP, like this using a plain text file:
temperature.php on raspberry pi:
<?php
echo shell_exec('/home/pi/CurrTemp');
temperature.php on Debian:
<?php
$temperature = file_get_contents('http://172.16.248.210/temperature.php');
echo $temperature;