Question

How can I make my own custom class be sortable using sort() for example?

I’ve been scanning the web to find any method of making a class Comparable like in Java but without much luck. I tried implementing __equals() but without luck. I’ve also tried with __toString(). My class looks like this:

class Genre {
    private $genre;
    private $count;
    ...
}

I want to sort them by count which is an Integer, in descending order… ($genre is a string)

Answer 1

You can create a custom sort method and use the http://www.php.net/manual/en/function.usort.php function to call it.

Example:

$Collection = array(..); // An array of Genre objects

// Either you must make count a public variable, or create
// an accessor function to access it
function CollectionSort($a, $b)
{
    if ($a->count == $b->count)
    {
        return 0;
    }
    return ($a->count < $b->count) ? -1 : 1;
}

usort($Collection, "CollectionSort");

If you’d like to make a more generic collection system you could try something like this

interface Sortable
{
    public function GetSortField();
}

class Genre implements Sortable
{
    private $genre;
    private $count;

    public function GetSortField()
    {
        return $count;
    }
}

class Collection
{
    private $Collection = array();

    public function AddItem($Item)
    {
        $this->Collection[] = $Item;
    }

    public function GetItems()
    {
        return $this->Collection;
    }

    public function Sort()
    {
        usort($this->Collection, 'GenericCollectionSort');
    }
}

function GenericCollectionSort($a, $b)
{
    if ($a->GetSortField() == $b->GetSortField())
    {
        return 0;
    }
    return ($a->GetSortField() < $b->GetSortField()) ? -1 : 1;
}

$Collection = new Collection();
$Collection->AddItem(...); // Add as many Genre objects as you want
$Collection->Sort();
$SortedGenreArray = $Collection->GetItems();