class f {
    function bar() { echo __METHOD__, '()', PHP_EOL; } 
    function __toString() { return 'v'; }
} 
class v { function __toString() { return 'c'; } } 
class m { function __toString() { return 'bar'; } } 
 
$c = 'f';
 
$${'v'} = new ${(string) new ${$v = 'v'}()}();
$$$$$$v->{(string) new m()}();