Array Iterator

filter_json.php

<?php

class AuthorFilter extends FilterIterator
{
    /**
     * @var Iterator
     */
    private $author;

    public function __construct(Iterator $iterator, $author)
    {
        parent::__construct($iterator);
        $this->author = $author;
    }

    public function accept()
    {
        return $this->current()->author == $this->author;
    }
}

$courses = file_get_contents('common/data/courses.json');
$courses = json_decode($courses);
$courses = new ArrayIterator($courses);
$courses = new AuthorFilter($courses, 'David Powers');

foreach ($courses as $course) {
    echo "$course->title author by $course->author<br />";
}

recursive_array.php

<?php

$products = [
    'Person' => ['Jacak', 'Tom', 'Cakkry'],
    'Animals' => ['Snack', 'Tigger', 'Lion'],
    'Sport' => ['Basketball', 'Fans' => ['One', 'tow', 'three']],
];

$products = new RecursiveArrayIterator($products);
$products = new RecursiveIteratorIterator($products, RecursiveIteratorIterator::SELF_FIRST);

foreach ($products as $key => $value) {
    $level = $products->getDepth() + 2;
    if ($products->hasChildren()) {
        echo "<h$level>$key</h$level>" . '<br />';
    } else {
        echo $value . '<br />';
    }
}