PHP multi-threaded PHP fsockopen solution

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Question:
Is there any way to implement multi-threading in php?

Suppose you are writing a PHP application based on multiple servers. The ideal situation is to send requests to multiple servers at the same time, rather than one after another.
Can it be achieved?
Answer:

When someone wants to implement concurrency functions, they usually think of using fork or spawn
threads, but when they find that php does not support multi-threading , you may change your mind and use some languages ​​that are not good enough, such as perl.

In fact, in most cases, you don't need to use fork or thread, and you will get better performance than using fork or thread.

Suppose you want to build a service to check n running servers to make sure they are still functioning normally. You might write code like the following:

$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);

It runs fine, but after fsockopen() analysis Expanding this code to manage a large number of servers would take a long time before hostname and a successful connection are established (or delay $timeout seconds).
So we have to abandon this code; we can establish an asynchronous connection - no need to wait for fsockopen to return connection status. PHP still needs to resolve the hostname (so it's more sensible to use the ip directly), but it will return immediately after opening a connection, and then we can connect to the next server.
There are two ways to achieve this; in PHP5, you can use the new stream_socket_client() function to directly replace fsocketopen(). For versions before PHP5, you need to do it yourself and use sockets extension to solve the problem.

The following is the solution in PHP5:

$hosts = array("host1.sample.com", "host2.sample.com", "host3.sample.com");
$timeout = 15;
$status = array();
$sockets = array();
foreach ($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 $errstr";
}
}
while (count($sockets)) {
$read = $write = $sockets;
$n = stream_select($read, $write, $e = null, $timeout);
if ($n > 0) {
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] .= $data;
}
}
foreach ($write as $w) {
$id = array_search($w, $sockets);
fwrite($w, "HEAD / HTTP/1.0rnHost: " . $hosts[$id] . "rnrn");
$status[$id] = "waiting for response";
}
} else {
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";
}

We use stream_select() to wait for sockets to open connection event. stream_select() calls the system's select(2) function to work: the first three parameters are the arrays of streams you want to use; you can read, write and get exceptions from them (for the three parameters respectively). stream_select() can wait for an event to occur by setting the $timeout (seconds) parameter - when the event occurs, the corresponding socket data will be written to the parameters you passed in.

The following is the implementation of PHP4.1.0 and later versions. If you have included sockets (ext/sockets) support when compiling PHP, you can use similar code as above, but you need to change the above streams/filesystem The functions of the function are implemented using the ext/sockets function. The main difference is that we use the following function instead of
stream_socket_client() to establish the connection:

// 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;
}

Now replace stream_select with socket_select() (), replace fread() with socket_read(), replace fwrite() with
socket_write(), replace fclose() with socket_close() and you can execute the script!
The advancement of PHP5 is that you can use stream_select() to process almost any stream - for example, you can use it to receive keyboard input through include
STDIN and save it into an array. You can also receive it and open it through proc_open() data in the pipeline.
If you want PHP4.3.x to have the function of processing streams, I have prepared a patch for you that allows fsockopen to work asynchronously. This patch is deprecated and will not appear in the officially released PHP version. I have included the implementation of the stream_socket_client() function in the patch, through which you can make your script compatible with
PHP5.

Related recommendations:

php multi-threading_PHP tutorial

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