$obj = new Obj(array(
	'opt1' => 'val1',
	'opt2' => array('o1' => 1, 'o2' => 2)
));

class Obj {
	protected $opt1 = 'val0';
	protected $opt2 = array('o1' => 0, 'o2' => 0, 'o3' => 0);
	protected $opt3 = 'val0';

	public function __constuct($param) {
		if (isset($param['opt1'])) $this->opt1 = $param['opt1'];
		if (isset($param['opt2'])) $this->opt2 = $param['opt2'];
		if (isset($param['opt3'])) $this->opt3 = $param['opt3'];
	}
        ...
}

$opt1 = 'val0';
$opt2 = array('o1' => 0, 'o2' => 0, 'o3' => 0);
$opt3 = 'val0';

$param = array(
		'opt1' => 'val1',
		'opt2' => array('o1' => 1, 'o2' => 2)
	);
    
foreach ($param as $k => $v) {
    $$k = $v;
}
print_r($opt1);
print_r($opt2);
print_r($opt3);