- var_dump: documentation ( source)
<?php
class Test{}
function returnTest(){return 'Test';}
var_dump(new ${!${''} = 'Test'}); // string literal name works
var_dump(new ${!${''} = returnTest()}); // function return value works
var_dump(new ${!${''} = (new class() { // method invokation from anonymous function expression works
function returnTest() : string{return 'Test';}
})->returnTest()});