is_null / isset

$cnt = 1000000;
$val1 = "fdasfdsafdsafdsa";
$val2 = null;

for ($i = 0; $i < $cnt; $i++) {
	// warmup loop
	$z = 1 + 1;
}
$st = getmicrotime();
print "warmup ".(getmicrotime() - $st)."\n";

$st = getmicrotime();
for ($i = 0; $i < $cnt; $i++) {
	$x = is_null($val1);
	$y = is_null($val2);
}
print "first test ".(getmicrotime() - $st)."\n";

$st = getmicrotime();
for ($i = 0; $i < $cnt; $i++) {
	$x = !isset($val1);
	$y = !isset($val2);
}
print "second test ".(getmicrotime() - $st)."\n";

exit;


warmup 2.0980834960938E-5
first test 0.19290900230408
second test 0.06994104385376