store.php

<?php
class Store
{
    public static $data = [];

    public static function set()
    {
        $params = static::parseArguments(func_get_args());
        static::$data = static::merge(static::$data, $params);
    }

    private static function parseArguments($args)
    {
        $result = [];
        $key = array_shift($args);
        
        if (count($args) === 1) {
            $result[$key] = $args[0];
        } else {
            $result[$key] = static::parseArguments($args);
        }
        
        return $result;
    }

    private static function merge($array1, $array2)
    {
        foreach ($array2 as $key => $value) {
            if (!is_array($array1)) {
                $array1 = [$array1];
            }

            if (is_array($value)) {
                if (!isset($array1[$key])) {
                    $array1[$key] = [];
                }
                $array1[$key] = static::merge($array1[$key], $value);
            } else {
                $array1[$key] = $value;
            }
        }

        return $array1;
    }
}

Store::set('user', 'profile', 'email', 'example@example.com');
Store::set('user', 'profile', 'nickname', 'dakatsuka');
Store::set('hoge', 'fuga');

print_r(Store::$data);

/**
Array
(
    [user] => Array
        (
            [profile] => Array
                (
                    [email] => example@example.com
                    [nickname] => dakatsuka
                )

        )

    [hoge] => fuga
)
**/