<?php

function invokeWithReference(StdClass &$class)
{
    // Create args array using reference
    $args = [$class];
    $obj = new ReflectionClass('xyz');
    return $obj->newInstanceArgs($args);
}

class xyz
{
    public $class;
    
    public function __construct(StdClass $class)
    {
        $this->class = $class;
    }

    public function setTest2()
    {
        $this->class->test2 = 'goodbye';
    }
}

$class = new StdClass;
$instance = invokeWithReference($class);

$class->test = 'hello';
$instance->setTest2();

echo $instance->class->test;
echo PHP_EOL;
echo $class->test2;