基于php实现长连接的方法与注意事项的问题
php可以通过set_time_limit(0);来取消php脚步超时限制,从而达到长连接的效果。
例子代码如下:
复制代码 代码如下:
echo "每隔3秒输出一次
";
set_time_limit(0); //保证php程序运行不超时退出
while(1) {
echo date("H:i:s")."
";
ob_flush();
flush(); //刷新并输出PHP缓冲数据
sleep(3); //延迟3秒
}
?>
示例代码2:
复制代码 代码如下:
set_time_limit(0);
header("Connection:Keep-Alive");
header("Proxy-Connection:Keep-Alive");
for($i=0;$i
print 'text'.$i.'
';
ob_flush();
flush();
sleep(1);
clearstatcache();
}
这里调用了ob_flush(); flush();来强制输出数据到缓冲区,这样就能在脚步返回之前及时返回数据到浏览器。另外不冲下flush和ob_flush的使用上有一些特别容易犯错的地方,造成无法刷新输出缓冲。
一. flush和ob_flush的正确顺序,正确应是,先ob_flush再flush,如下:
ob_flush();
flush();
如果Web服务器的操作系统是windows系统,那顺序颠倒或者不使用ob_flush()也不会出现问题。但是在Linux系统上就无法刷新输出缓冲。
二. 使用ob_flush()前,确保前面的内容大小足够4069字符。
一些Web服务器的output_buffering默认是4069字符或者更大,即输出内容必须达到4069字符服务器才会flush刷新输出缓冲,为了确保flush有效,最好在ob_flush()函数前有以下语句:
print str_repeat(" ", 4096);
以确保到达output_buffering值。
复制代码 代码如下:
for ($i=10; $i>0; $i--)
{
echo $i.'
';
ob_flush();
flush();
sleep(1);
}
ob_end_flush();

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