Online PHP editor | refs for GquSv

<?php function NC($x){ $y = array(); $y['test'] = $x; $returnThis = $y['test'] ?? "Foo"; return $returnThis; } NC(NULL); // I know this will return "Foo". /* But I have no clue about what these will return. */ var_dump(NC(0)); var_dump(NC(-1)); var_dump(NC("")); var_dump(NC(array()));