类中未定义的变量

I'm using a raspberry pi to control lightning in my apartment, and currently I'm writing a class to control RGB Leds. However, I'm having some troubles with it, and this particular problem is going to drive me crazy.

Whenever I call a function, setRed() for example, I get a notice that says Notice: Undefined variable: GPIORed in M:\wamp\www\LedControl\class.rgbcontrol.php on line 16

Shortened version of my class looks like this:

class RGBControl {

    var $GPIORed;
    var $GPIOGreen;
    var $GPIOBlue;

    public function __construct($red,$green,$blue) {
      $this->GPIORed = $red;
      $this->GPIOGreen = $green;
      $this->GPIOBlue = $blue;
    }


    public function setRed($power){
        shell_exec("echo \"$GPIORed=$power\" > /dev/pi-blaster");
    }

    public function setGreen($power){
        shell_exec("echo \"$GPIOGreen=$power\" > /dev/pi-blaster");
    }

    public function setBlue($power){
        shell_exec("echo \"$GPIOBlue=$power\" > /dev/pi-blaster");
    }
}

So here's basic usage, I'm defining the class with arguments 24,23,18 (the GPIO pins on the Raspberry Pi that my leds are connected to).

$LED = new RGBControl (24,23,18);

$LED->setRed($color[0] / 255);
$LED->setGreen($color[1] / 255);
$LED->setBlue($color[2] / 255);

But what am I doing wrong?

The lines like this:

shell_exec("echo \"$GPIOBlue=$power\" > /dev/pi-blaster");

are trying to resolve variables named $GPIOBlue and $power, but $GPIOBlue doesn't exist. You need to use $this to access instance member variables. For example,

shell_exec("echo \"{$this->GPIOBlue}=$power\" > /dev/pi-blaster");

public function setRed($power){
    shell_exec("echo \"$GPIORed=$power\" > /dev/pi-blaster");
}

You are trying to access the $GPIORed variable in the scope of the shell interpreter. It is only accessible through php. Like Dan mentioned, it's a scope reference issue. My bad.

I would recommend using a file operation instead of using shell_exec, partly because of security and partly because of readability.

file_put_contents("/dev/pi-blaster", "{$this->GPIORed}=$power
");