本节分享下，php多线程的几个例子，不使用fork或进程
以下代码实现：检查正在运行的n台服务器，以确定它们正常运转。
<?php
$hosts = array("host1.x.com", "host2.x.com", "host3.x.com");
$timeout = 15;
$status = array();
foreach ($hosts as $host) {
$errno = 0;
$errstr = "";
$s = fsockopen($host, 80, $errno, $errstr, $timeout);
if ($s) {
$status[$host] = "Connectedn";
fwrite($s, "HEAD / HTTP/1.0rnHost: $hostrnrn");
do {
$data = fread($s, 8192);
if (strlen($data) == 0) {
break;
}
$status[$host] .= $data;
} while (true);
fclose($s);
} else {
$status[$host] = "Connection failed: $errno $errstrn";
}
} //by www.jb200.com
print_r($status);
?>
以上代码在fsockopen()分析完hostname且建立一个成功的连接（或延时$timeout秒）之前，扩充这段代码来管理大量服务器将耗费很长时间。
放弃这段代码；可以建立异步连接-不需要等待fsockopen返回连接状态。
PHP仍然需要解析hostname（所以直接使用ip更加明智），不过将在打开一个连接之后立刻返回，继而就可以连接下一台服务器。
有两种方法可以实现；
1，PHP5中可以使用新增的stream_socket_client()函数直接替换掉fsocketopen()。
2，PHP5之前的版本，需要自己动手，用sockets进行扩展。
例子，PHP5中的解决方法：
<?php
$hosts = array("host1.x.com", "host2.x.com", "host3.x.com");
$timeout = 15;
$status = array();
$sockets = array();
/* Initiate connections to all the hosts simultaneously */
foreach ($hosts as $id => $host) {
$s = stream_socket_client("$host:80", $errno, $errstr, $timeout,
STREAM_CLIENT_ASYNC_CONNECT|STREAM_CLIENT_CONNECT);
if ($s) {
$sockets[$id] = $s;
$status[$id] = "in progress";
} else {
$status[$id] = "failed, $errno $errstr";
}
}
/* Now, wait for the results to come back in */
while (count($sockets)) {
$read = $write = $sockets;
/* This is the magic function - explained below */
$n = stream_select($read, $write, $e = null, $timeout);
if ($n > 0) {
/* readable sockets either have data for us, or are failed
* connection attempts */
foreach ($read as $r) {
$id = array_search($r, $sockets);
$data = fread($r, 8192);
if (strlen($data) == 0) {
if ($status[$id] == "in progress") {
$status[$id] = "failed to connect";
}
fclose($r);
unset($sockets[$id]);
} else {
$status[$id] .= $data;
}
}
/* writeable sockets can accept an HTTP request */
foreach ($write as $w) {
$id = array_search($w, $sockets);
fwrite($w, "HEAD / HTTP/1.0rnHost: "
. $hosts[$id] . "rnrn");
$status[$id] = "waiting for response";
}
} else {
/* timed out waiting; assume that all hosts associated
* with $sockets are faulty */
foreach ($sockets as $id => $s) {
$status[$id] = "timed out " . $status[$id];
}
break;
} //by www.jb200.com
}
foreach ($hosts as $id => $host) {
echo "Host: $hostn";
echo "Status: " . $status[$id] . "nn";
}
?>
用stream_select()等待sockets打开的连接事件。
stream_select()调用系统的select(2)函数来工作：
前面三个参数是你要使用的streams的数组；
可以对其读取，写入和获取异常（分别针对三个参数）。
stream_select()可以通过设置$timeout（秒）参数来等待事件发生-事件发生时，相应的sockets数据将写入你传入的参数。