PHP 输出缓冲区失败

Question

只是作为一个演示，试试下面的代码：

<?php
echo '<pre>';      
ob_end_flush();
for($i=0;$i<2;$i++) {
passthru("ping -n 8 127.0.0.1");
@ob_flush();
}
echo '</pre>';
?>

这是输出：

Pinging stackoverflow.com [64.34.119.12] with 32 bytes of data:
Reply from 64.34.119.12: bytes=32 time=28ms TTL=56
Reply from 64.34.119.12: bytes=32 time=29ms TTL=56
Reply from 64.34.119.12: bytes=32 time=29ms TTL=56
Reply from 64.34.119.12: bytes=32 time=28ms TTL=56

Ping statistics for 64.34.119.12:
    Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
    Minimum = 28ms, Maximum = 29ms, Average = 28ms

Pinging stackoverflow.com [64.34.119.12] with 32 bytes of data:
Reply from 64.34.119.12: bytes=32 time=28ms TTL=56
Reply from 64.34.119.12: bytes=32 time=27ms TTL=56
Reply from 64.34.119.12: bytes=32 time=26ms TTL=56
Reply from 64.34.119.12: bytes=32 time=29ms TTL=56

Ping statistics for 64.34.119.12:
    Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
    Minimum = 26ms, Maximum = 29ms, Average = 27ms

它实际上做了两次（来自“小于 2”循环）。如果您测试脚本，您会注意到执行第一个脚本需要几秒钟，然后它会立即将其全部输出。之后（第二个循环）它逐行进行。我的目标只是有一个输出，逐行执行，而不是缓冲任何输出，如下所示，除非它发生：

<?php
system("ping -n 8 127.0.0.1");
?>

注意：这是在装有 PHP 5 的 Windows 服务器上运行的。

Answer 1

所以，这里发生的事情是您的浏览器可能正在缓冲。我认为如果您查看数据包嗅探器，您的刷新可能正在工作。

为了确定，请致电flush() 和ob_flush()。

您永远无法清除所有缓冲区，因为 PHP 只知道自己的缓冲区。服务器可以缓冲，客户端几乎总是缓冲。