Comparing issues with values php

I have a problem with comparing 2 values and let 1 value change within the if statement. But ofcourse when I reload the page it picks up the first value again. I'm using this code to set some information in a database when a machine is turned on or off.

$urlMachineON = 'http://ift.tt/1GbRIuI';

// get content
$contentMachineON = file_get_contents($urlMachineON);

//remove first 2 characters
$truncate = substr($contentMachineON, 2);

//remove last 5 characters
$MachineOn = substr($truncate, 0, -5);
//MachineON can only be 1 or 0

$currentState = 2;

if ($MachineOn != $currentState)
{
$stmt = $conn->prepare("INSERT INTO machineactiviteit (Time, MachineStatus) VALUES(NOW(), ?)");

$stmt->bind_param('s', $MachineOn);

    if ($stmt->execute() === TRUE) 
    {
        $currentState = $MachineOn;
        echo 'success'; 
    }
    else 
    {
        echo $conn->error;
    }

$stmt->close(); 
}
elseif($MachineOn == $currentState)
{
    echo 'do nothing';
}

So when I do this he will always use the if statement since the $currentState and $MachineOn are always different from each other. In C# you have something like initalize component to set the value one time to a specific value. But I haven't found anything about that in php. So my question is can I set a value only once? Or should I solve this another way?

This is how it should work:

first attempt before: currentState = 2; MachineOn = 0; after: currentState= 0; MachineOn = 0;

second attempt before: currentState= 0; MachineOn = 0; after: currentState= 0; MachineOn = 0;

third attempt before: currentState= 0; MachineOn = 1; after: currentState= 1; MachineOn = 1;

(I can change the MachineOn value with a button).