I have an object, let's say it's like this:

class Foo {
    var $b, $a, $r;

    function __construct($B, $A, $R) {
        $this->b = $B;
        $this->a = $A;
        $this->r = $R;
    }
}

$f = new Foo(1, 2, 3);

I want to get an arbitrary slice of this object's properties as an array.

$desiredProperties = array('b', 'r');

$output = magicHere($foo, $desiredProperties);

print_r($output);

// array(
//   "b" => 1,
//   "r" => 3
// )