与非门

class NotAndGate extends Object{
    private $_key1;
    private $_key2;

    public function setKey1($value){
        $this->_key1 = $value;
    }

    public function setKey2($value){
        $this->_key2 = $value;
    }

    public function getOutput(){
        if (!$this->_key1 || !$this->_key2)
            return true;
        else if ($this->_key1 && $this->_key2)
            return false;
    }
}