Ok so here is my problem: I have the following code lines from a tutorial:
ok the code works perfectly but I dont understand something....

Why so, and not ? In our class we declared them as "$x" respectively "$y" and what that "$this" means?

thanx in advance, very n00b in this...

<?
// our class
class math
{
// our variables
var $x=1;
var $y=2;

// our functions
function sum()
{
// $this refers to our variables in this class
return $this->x + $this->y;
}
}

// declare a new class
$s = new math;

// show the total of x and y added together using the class function
echo "before changing x&y's values x+y = " . $s->sum();

// set class variables to new values
$s->x = 3;
$s->y = 4;

// show the total of x and y added together using the class function
echo "after changing x&y's values x+y = " . $s->sum();

?>