Example Casting.php

<?php

class Collection implements ArrayAccess, Arrayable, ...
{
  protected $items = [];
  
  public function __construct(array $items = [])
  {
    $this->items = $items;
  }
  
  ...
  
  public function __cast(array $items)
  {
    return new static($items);
  }
}

public function convert_me(Collection $items)
{
  var_dump($items);
}

$collection = new Collection([1,2,3]);

convert_me($collection);
convert_me([1,2,3]);