time.function.php

 '年',
        '2592000'=>'个月',
        '604800'=>'星期',
        '86400'=>'天',
        '3600'=>'小时',
        '60'=>'分钟',
        '1'=>'秒'
    );
    foreach ($f as $k=>$v)    {
        if (0 !=$c=floor($t/(int)$k)) {
            return $c.$v.'前';
        }
    }
}
//memery used...
$start_mem = memory_get_usage();
//code...
$end_mem = memory_get_usage();
$memused = $end_mem - $start_mem;
$memused_str = sprintf('memory usage: %01.9f MB', $memused/1024/1024);