Cache in files

Cache.php

<?php
/*
 * Usage [PHP >= 7.1]
 *
require_once __DIR__ . '/Cache.php';

$cache = new Cache(__DIR__ . '/cache.json');

$cache->set('key1', ['key1' => 'value1']);
print_r($cache->get('key1'));
*/

class Cache
{
    private $data;
    private $file;
    private $saved = false;

    public function __construct(string $file)
    {
        $this->file = $file;
        if (file_exists($file)) {
            $this->data = json_decode(file_get_contents($file), true);
        }
    }
    
    public function get(string $key, callable $newDataCallback = null, bool $saveInFile = false)
    {
        if (isset($this->data[$key])) {
            return $this->data[$key];
        }

        if ($newDataCallback && $newData = $newDataCallback()) {
            $this->set($key, $newData, $saveInFile);
            return $newData;
        }

        return null;
    }

    public function set(string $key, array $value, bool $saveInFile = false): void
    {
        $this->data[$key] = $value;
        if ($saveInFile) {
            $this->save();
        }
    }

    public function save(): void
    {
        if ($this->data) {
            file_put_contents($this->file, json_encode($this->data));
            $this->saved = true;
        }
    }

    public function __destruct()
    {
        if (!$this->saved) {
            $this->save();
        }
    }
}