SimpleCommand.php

<?php

class Lamp
{
    public function turnOn()
    {
        echo "I'm bright and cheerful light.\n";
    }

    public function turnOff()
    {
        echo "I am quiet and peaceful shadow\n";
    }
}

$lamp = new Lamp();
if ($argv[1] == 'ON') {
    $lamp->turnOn();
} else {
    if ($argv[1] == 'OFF') {
        $lamp->turnOff();
    } else {
        throw new \RuntimeException('I understand only ON/OFF command');
    }
}

if(method_exists($lamp, $argv[1])) { ... }