<?php

class Collection implements Iterator {
    private int $cursor = 0;

    public function __construct(
    	private array $items = []
    ) {}

	#[ReturnTypeWillChange]
    public function current(): int
    {
        return $this->items[$this->cursor];
    }
	#[ReturnTypeWillChange]
    public function key(): int
    {
        return $this->cursor;
    }

	#[ReturnTypeWillChange]
    public function next(): void
    {
        ++$this->cursor;
    }

	#[ReturnTypeWillChange]
    public function prev(): int {
        --$this->cursor;
    }

    public function rewind(): void {
        $this->cursor = 0;
    }

    public function valid(): bool
    {
        return isset($this->items[$this->cursor]);
    }
}

// Adding an array [1,2,3,4,5,6,7,8,9,10] to the collection
$collection = new Collection([1, 2, 3, 4, 5, 6, 7, 8, 9, 10]);

// Calculating the sum of the elements in the collection
$sum = 0;
foreach ($collection as $item) {
    $sum += $item;
}

echo "The sum of the elements in the collection is: $sum\n";