PHP - Ordenação 3 valores

< ?php

$a=9;
$b=10;
$c=6;

if($a > $b){
        $d = $a;
        $a = $b;
        $b = $d;
}
if($a > $c){
        $d = $a;
        $a = $c;
        $c = $d;
}
if($b > $c){
        $d = $b;
        $b = $c;
        $c = $d;
}
echo $a . "-" . $b ."-" . $c;
?>