Online PHP editor | refs for L8e35

<?php $x = NULL; echo "print_r of x:\n"; print_r($x); echo "\n\nis_null of x:\n"; print_r(is_null($x)); echo "\n\nisset of x:\n"; print_r(isset($x)); echo "print_r of y:\n"; print_r($y); echo "\n\nis_null of y:\n"; print_r(is_null($y)); echo "\n\nisset of y:\n"; print_r(isset($y));