转：链接地址
问题：
有没有办法在php中实现多线程呢？
假设你正在写一个基于多台服务器的php应用，理想的情况时同时向多台服务器发送请求，而不是一台接一台。
可以实现吗？
回答：
当有人想要实现并发功能时，他们通常会想到用fork或者spawn threads，但是当他们发现php不支持多线程的时候，大概会转换思路去用一些不够好的语言，比如perl。
其实的是大多数情况下，你大可不必使用fork或者线程，并且你会得到比用fork或thread更好的性能。
假设你要建立一个服务来检查正在运行的n台服务器，以确定他们还在正常运转。你可能会写下面这样的代码：
<?php
$hosts = array("host1.sample.com", "host2.sample.com", "host3.sample.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 $errstrn";
}
}
print_r($status);
?>
它运行的很好，但是在fsockopen()分析完hostname并且建立一个成功的连接（或者延时$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。
因此我们必须放弃这段代码；我们可以建立异步连接-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，继而我们就可以连接下一台服务器。
有两种方法可以实现；PHP5中可以使用新增的stream_socket_client()函数直接替换掉fsocketopen()。PHP5之前的 版本，你需要自己动手，用sockets扩展解决问题。
下面是PHP5中的解决方法：
<?php
$hosts = array("host1.sample.com", "host2.sample.com", "host3.sample.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;
}
}
foreach ($hosts as $id => $host) {
echo "Host: $hostn";
echo "Status: " . $status[$id] . "nn";
}
?>
我们用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；你可以对其读取，写入和获取异常（分别针对三个参数）。stream_select()可以通过设 置$timeout（秒）参数来等待事件发生-事件发生时，相应的sockets数据将写入你传入的参数。
下面是PHP4.1.0之后版本的实现，如果你已经在编译PHP时包含了sockets(ext/sockets)支持，你可以使用根上面类似的代 码，只是需要将上面的streams/filesystem函数的功能用ext/sockets函数实现。主要的不同在于我们用下面的函数代替 stream_socket_client()来建立连接：
<?php
// This value is correct for Linux, other systems have other values
define('EINPROGRESS', 115);
function non_blocking_connect($host, $port, &$errno, &$errstr, $timeout) {
$ip = gethostbyname($host);
$s = socket_create(AF_INET, SOCK_STREAM, 0);
if (socket_set_nonblock($s)) {
$r = @socket_connect($s, $ip, $port);
if ($r || socket_last_error() == EINPROGRESS) {
$errno = EINPROGRESS;
return $s;
}
}
$errno = socket_last_error($s);
$errstr = socket_strerror($errno);
socket_close($s);
return false;
}
?>
现在用socket_select()替换掉stream_select()，用socket_read()替换掉fread()，用 socket_write()替换掉fwrite()，用socket_close()替换掉fclose()就可以执行脚本了！
PHP5的先进之处在于，你可以用stream_select()处理几乎所有的stream-例如你可以通过include STDIN用它接收键盘输入并保存进数组，你还可以接收通过proc_open()打开的管道中的数据。
如果你想让PHP4.3.x自身拥有处理streams的功能，我已经为你准备了一个让fsockopen可以异步工作的patch。不赞成使用该补丁， 该补丁不会出现在官方发布的PHP版本中，我在补丁中附带了stream_socket_client()函数的实现，通过它，你可以让你的脚本兼容 PHP5。
附件：
documentation for stream_select()
documentation for socket_select()
patch for PHP 4.3.2 and script to emulate stream_socket_client(). (might work with later 4.3.x versions).
经测试，确实为多线程，弄了整个下午，终于弄好了~~~
$request = array("http://10.1.30.218/test/server.php","http://10.1.30.28/server.php ");
foreach($request as $r) {
$temp = parse_url($r);
$scheme[] = $temp['scheme'];
$hosts[] = $temp['host'];
$paths[] = isset($temp['path']) ? $temp['path'] : "" ;
}
//$hosts = array("www.bit.edu.cn ");
$timeout = 5;
$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 $errstr";
}
}
//print_r($sockets);print_r($status);
//*
// Now, wait for the results to come back in
while (count($sockets)) {
$read = $write = $sockets;
// This is the magic function – explained below
$ret = stream_select($read, $write, $e = null, $timeout);
if ($ret > 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[$id]);
} else {
if ($status[$id] == "in progress") {
$status[$id] = $data;
} else {
$status[$id] .= $data;
}
}
}
// writeable sockets can accept an HTTP request
foreach ($write as $w) {
$id = array_search($w, $sockets);
//fwrite($w, "HEAD / HTTP/1.0/r/nHost: " . $hosts[$id] . "/r/n/r/n");
fwrite($w, "GET /".$paths[$id]." HTTP/1.0/r/nHost: " . $hosts[$id] . "/r/n/r/n");
//$status[$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/r/n/r/n" . $status[$id];
}
break;
}
}
foreach ($hosts as $id => $host) {
echo "Host: $host/n";
echo '<pre>'.$status[$id].'</pre>';
/*
$pos = strpos($status[$id],"/r/n/r/n");
$content[$id] = substr($status[$id],$pos);
$status[$id] = substr($status[$id],0,$pos);
//echo "Status: " . $status[$id] . "/n/n";
echo $content[$id] . "/n/n" ;
*/
}
