PHP: __toString() and json_encode() not playing well together

Question

I\'ve run into an odd problem and I\'m not sure how to fix it. I have several classes that are all PHP implementations of JSON objects. Here\' an illustration of the issue

Answer 1

You're right the __toString() for the class B is not being called, because there is no reason to. So to call it, you can use a cast

class A
{
    protected $a;

    public function __construct()
    {
        $this->a = array( (string)new B, (string)new B );
    }

    public function __toString()
    {
        return json_encode( $this->a );
    }
}

Note: the (string) cast before the new B's ... this will call the _toString() method of the B class, but it won't get you what you want, because you will run into the classic "double encoding" problems, because the array is encoded in the B class _toString() method, and it will be encoded again in the A class _toString() method.

So there is a choice of decoding the result after the cast, ie:

 $this->a = array( json_decode((string)new B), json_decode((string)new B) );

or you're going to need to get the array, by creating a toArray() method in the B class that returns the straight array. Which will add some code to the line above because you can't use a PHP constructor directly (you can't do a new B()->toArray(); ) So you could have something like:

$b1 = new B;
$b2 = new B;
$this->a = array( $b1->toArray(), $b2->toArray() );