If you want to retrieve the class vars from within the class itself, use $this.
<?php
class Foo {
    var $a;
    var $b;
    var $c;
    var $d;
    var $e;
    function GetClassVars()
    {
        return array_keys(get_class_vars(get_class($this))); // $this
    }
}
$Foo = new Foo;
$class_vars = $Foo->GetClassVars();
foreach ($class_vars as $cvar)
{
    echo $cvar . "<br />\n";
}
?>
Produces, after PHP 4.2.0, the following:
a
b
c
d
e