echo "\r\n";
$i = -1;
echo "18)";
echo $a[++$i] + $a[++$i];
echo "\r\n";
$i = 0;
echo "19)";
echo $a[$i] + ($a[$i] = 400);
echo "\r\n";
$a[0] = 100;
echo "20)";
echo ($a[$i] = 400) + $a[$i];
echo "\r\n";
class c
{
var $val = 10;
static $stat = 20;
}
echo "21)";
echo c::$stat + (c::$stat = 200);
echo "\r\n";
echo "22)";
echo (c::$stat = 300) + c::$stat;
echo "\r\n";
$c = new c();
echo "23)";
echo $c->val + ($c->val = 200);
echo "\r\n";
echo "24)";
echo ($c->val = 300) + $c->val;
echo "\r\n";