example.php

<?php

class Collection implements Castable
{
  protected $items = [];
  
  public function __construct(array $items = [])
  {
    $this->items = $items;
  }
  
  // ... 
}

class AnotherClass
{
  public static function DoSomething(Collection $collection)
  {
    // ...
    return $collection->sum();
  }
}

// Acceptable Parameters: Collection | array
$another = AnotherClass::DoSomething([1,2,3]);