内存使用量

function getMemoryUsage($precision = 2)
    {
        $size = memory_get_usage(true);
        $unit = ['b', 'kb', 'mb', 'gb', 'tb', 'pb'];
        return round($size / pow(1024, ($i = floor(log($size, 1024)))), $precision) . ' ' . $unit[$i];
    }