How to use default value if unset parameter is an object

Question

I need to build a method where an object is passed as parameter. This method is using PHP "instanceof" shortcut.

//Class is setting a coordinate.
class PointCartesien {
    //PC props
    private $x;
    private $y;

    //Constructor
    public function __construct($x, $y) {
        $this->x = $x;
        $this->y = $y;
    }

    //The method in question... It makes the coordinate rotate using (0,0) as default and $pc if set.
    //Rotation
    public function rotate($a, PointCartesien $pc) {
        //Without $pc, throws error if empty.
        if(!isset($pc)) {
            $a_rad = deg2rad($a);

            //Keep new variables
            $x = $this->x * cos($a_rad) - $this->y * sin($a_rad);
            $y = $this->x * sin($a_rad) - $this->y * cos($a_rad);

            //Switch the instance's variable
            $this->x = $x;
            $this->y = $y;
            return true;
        } else {
            //...
        }
    }
}

Using isset() throws an error. The way I want it to work is by setting $pc parameters rotate($a, PointCartesien $pc = SOMETHING) to (0,0) as default. How would I do that?

Answer 1

You're requiring the $pc parameter for your function call, so you'll get an error before you ever reach the isset() check. Try public function rotate($a, PointCartesien $pc = null) {, then use the is_null check in place of isset.