PHP example: bool isset(mixed, ...)

$x = ''; if (isset($x, $y)) { echo "\$x and \$y are set and not null.\n"; // Never executed } else { echo "\$x or \$y is not set or is null.\n"; } $y = ''; if (isset($x, $y)) { echo "\$x and \$y are set and not null.\n"; } else { echo "\$x or \$y is not set or is null.\n"; // Never executed }