class Arr
{
    public static function setValue(&$data, $path, $value)
    {
        $temp = &$data;
        foreach ($path as $key) $temp = &$temp[$key];        
        $temp = $value;
        return $value;
    }

    public static function getValue(&$data, $path, $value)
    {
        $temp = &$data;
        foreach ($path as $key) $temp = &$temp[$key];
        return $temp;
    }

    public static function incValue(&$data, $path, $value)
    {
        $temp = (int)self::getValue($data, $path, $value)+$value;
        self::setValue($data, $path, $temp);
    }
}

$d=array();
Arr::incValue($d,array("the","next","value"),10);
echo '
'.json_encode($d, JSON_PRETTY_PRINT);

/*
{
    "the": {
        "next": {
            "value": 10
        }
    }
}
*/