mock_objects.php
public function returnsByReference($method, &$reference, $args = false)
    {
        $this->dieOnNoMethod($method, 'set return reference');
        $this->actions->register($method, $args, new SimpleByReference($reference));
    }
public function returnsByReference($method, &$reference, $args = false)
    {
        $this->dieOnNoMethod($method, 'set return reference');
        $this->actions->register($method, $args, new SimpleByReference($reference));
    }
Sets a return for a parameter list that will be passed by reference for all calls.

@param string $method       Method name.
@param mixed $reference     Result of the call will be this object.
@param array $args          List of parameters to match including wildcards.