function minmax (&$a,&$b)  {
  if ($a > $b) {
    $t=$a; $a=$b; $b=$t;
  }
}

$x=10;
$y=3;
echo "x=",$x,",y=",$y,"<BR>\n";
minmax($x,$y);
echo "x=",$x,",y=",$y,"<BR>\n";

?>