An array, an object, or delimited values in a string. Technically theres also globals but we won't talk about that.
As far as your pseudo code goes, it's pretty close to reality.
list($a,$b,$c) = test();
function test()
{
//.....
return array($a,$b,$c);
}
You could also pass your variables to your function by reference, and let the function populate them.
test($a, $b, $c);
function test(&$a, &$b, &$c)
{
// .....
$a = $x;
$b = $y;
$c = $z;
return;
}
Edit - Forgot about passing by reference.