php sleep 小于1秒

    php 用sleep(s)來(lái)進(jìn)行停頓，那么小于1秒的停頓怎么弄呢？那就是usleep ，不過(guò)，usleep只能在unix（linux）系統(tǒng)下運(yùn)行哦。
    echo "\n\rsleep begin:".microtime_float();
    sleep(1);
    echo "\n\rsleep 1 s:".microtime_float();
    sleep(2);
    echo "\n\rsleep 2 s:".microtime_float();
    //
    echo "\n\rusleep begin:".microtime_float();
    usleep(50*1000);
    echo "\n\rusleep 50 ms:".microtime_float();
    usleep(990*1000);
    echo "\n\rusleep 990 ms:".microtime_float();
    ~
    數(shù)據(jù)結(jié)果如下
    sleep begin:1381225780.5979
    sleep 1 s:1381225781.5991
    sleep 2 s:1381225783.6
    usleep begin:1381225783.6
    usleep 50 ms:1381225783.651
    usleep 990 ms:1381225784.6419
    microtime_float函數(shù)如下
    function microtime_float(){
    list($usec, $sec) = explode(" ", microtime());
    return ((float)$usec + (float)$sec);
    }