# PHP Object Iteration

PHP provides a way for objects to be defined so it is possible to iterate through a list of items, for example with a `foreach` statement.

---

## 1. Simple Iteration
By default, all visible properties will be used for the iteration.

```php
class MyClass {
    public $var1 = 'value 1';
    public $var2 = 'value 2';
    public $var3 = 'value 3';

    protected $protected = 'protected var';
    private   $private   = 'private var';

    function iterateVisible() {
       echo "MyClass::iterateVisible:\n";
       foreach ($this as $key => $value) {
           print "$key => $value\n";
       }
    }
}

$class = new MyClass();

foreach($class as $key => $value) {
    print "$key => $value\n";
}
echo "\n";

$class->iterateVisible();
```

## 2. The Iterator Interface
To customize object iteration, you can implement the `Iterator` interface. It requires 5 methods:

*   `current()`: Returns the current element.
*   `key()`: Returns the key of the current element.
*   `next()`: Moves forward to next element.
*   `rewind()`: Rewinds the Iterator to the first element.
*   `valid()`: Checks if current position is valid.

```php
class myIterator implements Iterator {
    private $position = 0;
    private $array = array(
        "firstelement",
        "secondelement",
        "lastelement",
    );

    public function __construct() {
        $this->position = 0;
    }

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

    public function current(): mixed {
        return $this->array[$this->position];
    }

    public function key(): mixed {
        return $this->position;
    }

    public function next(): void {
        ++$this->position;
    }

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

$it = new myIterator;

foreach($it as $key => $value) {
    var_dump($key, $value);
}
```

## 3. IteratorAggregate
Alternatively, you can implement the `IteratorAggregate` interface, which requires just one method `getIterator()`. This is often easier if you just want to return an array iterator or a generator.

```php
class MyCollection implements IteratorAggregate {
    private $items = [1, 2, 3];

    public function getIterator(): Traversable {
        return new ArrayIterator($this->items);
    }
}
```

[[programming/php/php]] [[programming/php/php-classes]]