tiny php class to store tiny amounts of persistent data into a JSON file

GlobalStorage.php

<?php

// helper class to store tiny amounts of data that should persist across sessions
class GlobalStorage {

    private static $instance;

    public static function getInstance() {
        if(!self::$instance) {
            self::$instance = new GlobalStorage();
        }
        return self::$instance;
    }


    private $data;
    private $storage;

    public function __construct() {
        $this->storage = __DIR__ . '/../data/global.json';
        $fileContent = is_file($this->storage) ? file_get_contents($this->storage) : false;
        $this->data = $fileContent === false ? array() : json_decode($fileContent, true);
    }

    public function get($key, $default = null) {
        return array_key_exists($key, $this->data) ? $this->data[$key] : $default;
    }

    public function set($key, $value, $instantSave = false) {
        $this->data[$key] = $value;
        if($instantSave) {
            $this->persist();
        }
    }

    public function persist() {
        file_put_contents($this->storage, json_encode($this->data, JSON_PRETTY_PRINT));
    }

}