$storage = new \IvoPetkov\ObjectStorage('path/to/the/data/dir/');

// Save data
$storage->set([
    'key' => 'books/1449392776',
    'body' => 'book 1449392776 content in pdf format',
    'metadata.title' => 'Programming PHP',
    'metadata.authors' => '["Kevin Tatroe", "Peter MacIntyre", "Rasmus Lerdorf"]',
    'metadata.year' => '2013'
]);

// Retrieve data
$result = $storage->get([
    'key' => 'books/1449392776',
    'result' => ['body', 'metadata.title']
]);
// Array
// (
//     [body] => 'book 1449392776 content in pdf format'
//     [metadata.title] => 'Programming PHP'
// )