<?
class test {
    protected static $var = 'hello';

    public function test2() {
        if(empty($this->var)) {
            echo 'this empty<BR>';
        }
        else {
            echo 'this populated<BR>';
        }
        if(empty(self::$var)) {
            echo 'self empty<BR>';
        }
        else {
            echo 'self populated<BR>';
        }
    }

    public static function test1() {
        echo "this not avail.<bR>";
        if(empty(self::$var)) {
            echo 'self empty<BR>';
        }
        else {
            echo 'self populated<BR>';
        }
    }
}

test::test1();
$temp = new test();
$temp->test2();