kvstore.php

<?php

function kvstore ($file, $init = NULL) {
    static $stores = [];
    $store = @$stores[$file];
    if (!$store) {
        $prev = @file_get_contents($file);
        if (!$prev) {
            if ($init) {
                $prev = json_encode((object) $init());
            } else {
                $prev = '{}';
            }
        }
        $next = json_decode($prev);
        $prev = json_decode($prev);
        $stores[$file] = $store = $next;
        register_shutdown_function(function () use ($file, $prev, $next) {
            if ($prev != $next) {
                file_put_contents($file, json_encode($next), LOCK_EX);
            }
        });
    }
    return $store;
}