The new spaceship operator introduced in PHP 7 can be used to compare two expressions. Here’s a little example showing a custom sorting function using usort which first orders the given array by name, then by category, alphabetically.
usort($mylist, function($a, $b) {
if($a->category == $b->category) {
return $a->name <=> $b->name;
}
return $a->category <=> $b->category;
});