PHP 7.4.0 alpha 2 Released

socket_select

(PHP 4 >= 4.1.0, PHP 5, PHP 7)

socket_select与えられたソケットの配列に対し、指定した有効時間で select() システムコールを実行する

説明

socket_select ( array &$read , array &$write , array &$except , int $tv_sec [, int $tv_usec = 0 ] ) : int

socket_select() はソケットの配列を受け取り、 それらの状態が変化するまで待ちます。BSD のソケットについての知識がある方なら、 これらのソケットの配列が、いわゆるファイル記述子セットであることがご理解いただけるでしょう。 3 つの独立した配列でソケットリソースを監視します。

パラメータ

read

配列 read に挙げられたソケットでは、 文字が読み込み可能になっているかどうか(厳密に言うと、読み込みが ブロックされていないかどうか - 実際には、ソケット記述子はファイルの 終端でも有効です。そのような場合、socket_read() は長さゼロの文字列を返します)を監視します。

write

配列 write に挙げられたソケットでは、 書き込みがブロックされていないかどうかを監視します。

except

配列 except に挙げられたソケットでは、 例外を監視します。

tv_sec

tv_sec および tv_usec は、ともにタイムアウトを指定するパラメータです。 タイムアウトは、socket_select() が結果を返すまでの経過時間の最大値です。 tv_sec はゼロにすることも可能で、そうすると socket_select() は結果をすぐに返します。 これはポーリングをする際に有用です。tv_secNULL(タイムアウトしない)を指定すると、 socket_select() は無期限にブロックします。

tv_usec

警告

終了時に配列は書き換えられ、 どのソケットの状態が変わったのかがわかるようになります。

socket_select() のすべての配列を設定する必要はありません。 使用しないものについては空の配列や NULL をかわりに指定しておくことが可能です。 また、これらの配列は参照渡し であり、 socket_select() をコールした後でその中身が書き換えられていることに注意しましょう。

注意:

現状の Zend Engine の制限により、関数の参照渡しパラメータに NULL のような定数値を直接渡すことができません。一時的な変数を使用するか、 あるいは一番左に一時変数を使用する式を使用してください。

例1 socket_select() での NULL の使用

<?php
$e 
NULL;
socket_select($r$w$e0);
?>

返り値

成功した場合は、socket_select() は配列内で 変化のあったソケットリソースの数を返します。もし何かがおこる前に タイムアウト時間が経過した場合は、ゼロを返すことになります。 エラー時には FALSE が返されます。エラーコードは socket_last_error() で取得可能です。

注意:

エラーかどうかを調べる際には、必ず === 演算子を 使用するようにしましょう。socket_select() は 0 を返す場合もあり、このような場合に == を用いて比較すると、エラーと判定されてしまいます。

例2 socket_select() の返す結果を知る

<?php
$e 
NULL;
if (
false === socket_select($r$w$e0)) {
    echo 
"socket_select() は失敗しました。原因: " .
        
socket_strerror(socket_last_error()) . "\n";
}
?>

例3 socket_select() の例

<?php
/* 読み込み用の配列を準備する */
$read   = array($socket1$socket2);
$write  NULL;
$except NULL;
$num_changed_sockets socket_select($read$write$except0);

if (
$num_changed_sockets === false) {
    
/* エラー処理 */
} else if ($num_changed_sockets 0) {
    
/* すくなくともひとつのソケットで、何らかの出来事が起こっています */
}
?>

注意

注意:

ソケットの実装によっては、取り扱いに注意すべきものがあることを知っておいてください。 基本的なルールは以下のとおりです。

  • 基本的に socket_select() のタイムアウトは 指定しないように心がけましょう。もしデータがなかった場合に、 プログラム側でそれを判定できなくなってしまいます。タイムアウトに 依存しているコードは移植性が悪く、デバッグが困難です。
  • socket_select() のコール後に値をチェックして 適切に処理するつもりがないソケットリソースは、決して配列に追加してはいけません。 socket_select() から値が返ってきたあとは、 配列内のすべてのソケットリソースをチェックする必要があります。 すべての書き込み用ソケットは書き込める必要がありますし、 またすべての読み込み用ソケットは読み込める必要があります。
  • 配列で返されたソケットに対して読み込み/書き込みをする場合には、 指定したデータを必ずしもすべて読み込み/書き込みするとは限らないことを 知っておいてください。たった 1 バイトしか読み込み/書き込みが できなかった場合にも対処できるよう準備しておきましょう。
  • ほとんどのソケット実装で、except でキャッチできる 例外はただひとつ、すなわちソケットが受け取ったデータが帯域外で あったということだけです。

参考

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User Contributed Notes 22 notes

up
40
vardhan ( at ) rogers ( dot ) com
13 years ago
A simple PHP script using socket_select() to manage multiple connections.
connect using "telnet localhost 9050". it broadcasts your messages that you send through telnet to other users connected to the server -- sort of like a chat script

#!/usr/local/bin/php
<?php

    $port
= 9050;
   
   
// create a streaming socket, of type TCP/IP
   
$sock = socket_create(AF_INET, SOCK_STREAM, SOL_TCP);
   
   
// set the option to reuse the port
   
socket_set_option($sock, SOL_SOCKET, SO_REUSEADDR, 1);
   
   
// "bind" the socket to the address to "localhost", on port $port
    // so this means that all connections on this port are now our resposibility to send/recv data, disconnect, etc..
   
socket_bind($sock, 0, $port);
   
   
// start listen for connections
   
socket_listen($sock);

   
// create a list of all the clients that will be connected to us..
    // add the listening socket to this list
   
$clients = array($sock);
   
    while (
true) {
       
// create a copy, so $clients doesn't get modified by socket_select()
       
$read = $clients;
       
       
// get a list of all the clients that have data to be read from
        // if there are no clients with data, go to next iteration
       
if (socket_select($read, $write = NULL, $except = NULL, 0) < 1)
            continue;
       
       
// check if there is a client trying to connect
       
if (in_array($sock, $read)) {
           
// accept the client, and add him to the $clients array
           
$clients[] = $newsock = socket_accept($sock);
           
           
// send the client a welcome message
           
socket_write($newsock, "no noobs, but ill make an exception :)\n".
           
"There are ".(count($clients) - 1)." client(s) connected to the server\n");
           
           
socket_getpeername($newsock, $ip);
            echo
"New client connected: {$ip}\n";
           
           
// remove the listening socket from the clients-with-data array
           
$key = array_search($sock, $read);
            unset(
$read[$key]);
        }
       
       
// loop through all the clients that have data to read from
       
foreach ($read as $read_sock) {
           
// read until newline or 1024 bytes
            // socket_read while show errors when the client is disconnected, so silence the error messages
           
$data = @socket_read($read_sock, 1024, PHP_NORMAL_READ);
           
           
// check if the client is disconnected
           
if ($data === false) {
               
// remove client for $clients array
               
$key = array_search($read_sock, $clients);
                unset(
$clients[$key]);
                echo
"client disconnected.\n";
               
// continue to the next client to read from, if any
               
continue;
            }
           
           
// trim off the trailing/beginning white spaces
           
$data = trim($data);
           
           
// check if there is any data after trimming off the spaces
           
if (!empty($data)) {
           
               
// send this to all the clients in the $clients array (except the first one, which is a listening socket)
               
foreach ($clients as $send_sock) {
               
                   
// if its the listening sock or the client that we got the message from, go to the next one in the list
                   
if ($send_sock == $sock || $send_sock == $read_sock)
                        continue;
                   
                   
// write the message to the client -- add a newline character to the end of the message
                   
socket_write($send_sock, $data."\n");
                   
                }
// end of broadcast foreach
               
           
}
           
        }
// end of reading foreach
   
}

   
// close the listening socket
   
socket_close($sock);
?>
up
3
malcolm.murphy
2 years ago
This was mentioned by [Viorel] above but I think it warrants being repeated...

The example provided by [vardhan ( at ) rogers ( dot ) com], while otherwise exceptional, uses the value int(0) for $tv_sec which will cause the iteration to loop as fast as possible, consequently using up any available CPU time.

*** Ideally, $tv_sec should always be set to NULL ***, especially if you are using socket_select in a loop. If you must temporarily stop listening for events to perform another task, then the timeout should be as high as possible to reduce CPU strain (another note suggested preventing 100% CPU usage by setting a low $tv_usec value, which only makes the problem slightly less worse but does not solve it).

Setting the timeout to an explicit null value is basically the same as setting it to infinite. The script will only execute the while loop once every time there is an event.
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4
John
9 years ago
The way the document describes socket_select()'s handling of sockets polled for read is rather obscure.

It says that it checks to see if reading would not "block," but the overall description of socket_select() says it checks for a change in blocking status. Unfortunately, these are in conflict.

If a socket already has data in the buffer, calling socket_select() on that socket would never return (assuming null timeout), and would block forever. :-( This is because the blocking status wouldn't change. It simply stays "non-blocking"

It is important to remember NOT to select() on a socket which may already have data available.

An example...
<?php
//... $socket is already here...
$done = false;
$n = 0;
do{
   
$tmp = 0;
   
$r = $w = $e = array();
   
$r = array($socket);
   
socket_select($r,$w,$e,null);
   
$n = socket_recv($socket, $tmp, 1024, 0);

   
//$done = true; //Something determines that we are done reading...
}while(!$done);
?>
This MAY NOT work... socket_select() is always being called... but we may have data in the input buffer.

We need to ensure that the last time we read, nothing was read... (empty buffer)
<?php
//... $socket is already here...
$done = false;
$n = 0;
do{
   
$tmp = 0;
   
$r = $w = $e = array();
   
$r = array($socket);
    if(
$n === 0) socket_select($r,$w,$e,null);
   
$n = socket_recv($socket, $tmp, 1024, 0);

   
//$done = true; //Something determines that we are done reading...
}while(!$done);
?>
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2
qartis at gmail dot com
11 years ago
In regards to the code posted by vardhan ( at ) rogers ( dot ) com, it appears that on the following line:
        if (socket_select($read, $write = NULL, $except = NULL, 0) < 1)
the timeout parameter is accidentally set to 0, rather than NULL. This means that the select call will return immediately rather than blocking indefinitely.

Change the socket_select line to the following for great success:
        if (socket_select($read, $write = NULL, $except = NULL, NULL) < 1)
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3
antti r
3 years ago
as of 12/2015 and php 5.3.3, the socket_select() maximum sockets is still 1024 and not risable by process file limits (bash ulimit -n). PHP new compilation is required to raise the limits. Or one might rather choose forking or multiple binaries.
up
1
calimero dot NOSPAM at NOSPAM dot creatixnet dot com
16 years ago
Please note that the timeout parameter has important side-effects on the CPU usage of your script.

Setting the timeout to 0 will make your CPU looping without any time to have some rest and handle other running processes on your system, causing the system load to increase heavily while your script is running.

Personnaly, I use a value of 15 ms for this parameter. this ensures a good listening frequency while letting your system load clear.

Example :
$read = array($ListeningSocket);
$num_changed_sockets = socket_select($read, $write = NULL, $except = NULL, 0, 10);

Hope this helps.
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2
Viorel
6 years ago
Probably you will want to use

// get a list of all the clients that have data to be read from
// if there are no clients with data, go to next iteration
        if (socket_select($read, $write = NULL, $except = NULL, NULL) < 1)
            continue;
           
instead 
        if (socket_select($read, $write = NULL, $except = NULL, 0) < 1)
            continue;
which will hang your CPU to 100% (return immediate if nothing to be done)
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1
jean at briskula dot si
8 years ago
As it was already said, some clients need \0 character to end transmission, for example Flash's XMLSocket.

You should also be prepared to read less data than you have requested.

Here is an example of a socket buffer - it's an array which has socket resources for keys and an array of a timestamp and recieved data as values.

I find that the best practice for sending data is trailing it with a new line and zero character (\n\0), because you will probably have different types of clients which behave differently for reading data from sockets. Some need a \n to fire an event, some need \0.

For recieving data, sometimes you will get splitted data - this can hapen because the buffer is full (in my example 8192 bytes) or it just gets broken during transmission in lower levels.

Sometimes you can read two messages at once, but they have a zero character in between, so you can just use preg_split() to split the messages. The second message may not be complete, so you add it to your buffer.

<?php
   
const message_delimiter = "\n\0";

   
/*
     * Clear socket buffers older than 1 hour
     */
   
function clear_buffer() {
        foreach(
$this->buffer as $key=>$val) {
            if(
time() - $val['ts'] > 3600) {
                unset(
$this->buffer[$key]);
            }
        }
    }

   
/*
     * Add data to a buffer
     */
   
function buffer_add($sock,$data) {
        if(!isset(
$this->buffer[$sock])) {
           
$this->buffer[$sock]['data'] = '';
        }

       
$this->buffer[$sock]['data'] .= $data;
       
$this->buffer[$sock]['ts'] = time();
    }

    function
buffer_get($sock) {
       
// split buffer by the end of string
       
$lines = preg_split('/\0/',$this->buffer[$sock]['data']);

       
// reset buffer to the last line of input
        // if the buffer was sent completely, the last line of input should be
        // an empty string
       
$this->buffer[$sock]['data'] = trim($lines[count($lines)-1]);

        if(!empty(
$this->buffer[$sock]['data'])) {
           
debug("buffer is not empty for $sock, len: ".strlen($this->buffer[$sock]['data']));
        }

       
// remove the last line of input (incomplete data)
        // parse any complete data
       
unset($lines[count($lines)-1]);

       
// return only the fully sent data
       
return $lines;
    }

    function
read(&$sock,$len=8192,$flag=MSG_DONTWAIT) {
       
$lines = array();

       
$this->clear_buffer();

       
$bytes_read = @socket_recv($sock,$read_data,$len,$flag);

        if (
$bytes_read === false || $bytes_read == 0) {
            return
false;
        } else {
           
debug("recv: $read_data");
           
$this->buffer_add($sock,$read_data);
            return
$this->buffer_get($sock);
        }
    }

   
/*
     * Write to a socket
     * add a newline and null character at the end
     * some clients don't read until new line is recieved
     *
     * try to send the rest of the data if it gets truncated
     */
   
function write(&$sock,$msg) {
       
$msg = $msg.self::message_delimiter;
       
$length = strlen($msg);
        while(
true) {
           
$sent = @socket_write($sock,$msg,$length);
            if(
$sent <= 0) {
                return
false;
            }
            if(
$sent < $length) {
               
$msg = substr($msg, $sent);
               
$length -= $sent;
               
debug("Message truncated: Resending: $msg");
            } else {
                return
true;
            }
        }
        return
false;
    }
?>
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1
magemerlin at list dot ru
9 years ago
If you using a Flash client - you should know some specific features:

1) when client connects to the server - it is sending to you "<policy-file-request/>"."\0" string. Server should answer an XML policy file, then disconnect from this client. Code is something like

if ('<policy-file-request/>'==substr($data, 0, 22))
                {
                    echo "policy requset.\n";
                    flush();ob_flush();
                    $msg = '<'.'?xml version="1.0"?>
<!DOCTYPE cross-domain-policy SYSTEM "http://www.macromedia.com/xml/dtds/cross-domain-policy.dtd">
<cross-domain-policy>
<allow-access-from domain="*" to-ports="*" />
</cross-domain-policy>'."\0";
                    echo "Say to client (crossdomain.xml) ... ";
                    flush();ob_flush();
                    socket_write($read_sock, $msg, strlen($msg));
                    echo "OK\n";
                    flush();ob_flush();
                   
                    echo "Closing ... ";
                    flush();ob_flush();
                    socket_close($read_sock);
                    echo "OK\n";
                    flush();ob_flush();
                }
                else
                {
// here is normal IO operations with client
}

2) every output to client should be ended with "\0" (if using XMLSocket in Flash client) - otherwise flash will not generate onData event

Russian examples is there - http://www.flasher.ru/forum/showpost.php?p=901346&postcount=7
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-1
renmengyang567 at gmail dot com
2 months ago
<explain>
A simple socket-select case ^_^

<?php
$sock
= socket_create(AF_INET, SOCK_STREAM, getprotobyname('tcp'));
socket_set_option($sock, SOL_SOCKET, SO_REUSEADDR, 1);
socket_bind($sock, '127.0.0.1',5000);
socket_listen($sock,1024);
$all_sock[(int)$sock] = $sock;

while (
true) {
   
$read = $write = $except = [];
   
$tv_sec = 5;
   
$tv_usec = 5000;
   
$read = $all_sock;
   
   
$changed = socket_select($read, $write, $except, $tv_sec, $tv_sec);

    if (
false == $changed)
        print
"[error]socket_select() failed
        ("
.socket_strerror(socket_last_error()) . ")\n";

    if (
$changed < 1)
       continue;

   
//var_dump($read);
    //sleep(2);
   
foreach ($read as $rsock) {
       
// 服务端连接
       
if ($rsock === $sock) {
           
$client = socket_accept($sock);
           
$all_sock[(int)$client] = $client;
       
        } else {
//客户端连接
           
$msg= socket_read($rsock, 400,PHP_NORMAL_READ);
            if (
$msg !== '') {
               
var_dump($msg);
            }
        }
    }
}
socket_close($sock);
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0
simon dot riget at gmail dot com
5 years ago
A verry simple HTTP webserver written in PHP
Run it in the shell with php <name of file> and test in in the browser with <server address>:8080/test

<?php
 
// Reduce the amount of warnings displayed
 
error_reporting(E_ALL ^ E_NOTICE);

 
// Set up socket for listening
 
$host_socket = socket_create(AF_INET, SOCK_STREAM, SOL_TCP);
  if(!
$host_socket) die("Failed to start event server. socket_create: ". socket_strerror(socket_last_error())."\n");

 
// set the option to reuse the port
 
if(! socket_set_option($host_socket, SOL_SOCKET, SO_REUSEADDR, 1) )
    die(
"Failed to start event server. socket_set_option: ". socket_strerror(socket_last_error())."\n");

 
// bind host socket to localhost or 0.0.0.0 on port 8080
 
if(! socket_bind($host_socket,"0.0.0.0",8080) )
    die(
"Failed to start event server. socket_bind: ". socket_strerror(socket_last_error())."\n");

 
// start listening for connections
 
if(! socket_listen($host_socket,10) )
    die(
"Failed to start event server. socket_listen: ".socket_strerror(socket_last_error())."\n");

  while (
true) {
   
// Make list of sockets to listen for changes in, including host
   
$read = array($host_socket);
        
   
// get a list of all the clients that have data to be read from
   
$ready=@socket_select($read, $write = NULL, $except = NULL,0);
    if (
$ready=== false)
      die(
"Failed to listen for clients: ". socket_strerror(socket_last_error()));

   
// a client request service
   
elseif($ready>0){
     
// accept new client
     
$newsocket = socket_accept($host_socket);

     
// Read from socket
     
$input = socket_read($newsocket, 1024);
      if(
$input){
        unset(
$client_header);
       
// Read headers; Split into safe lines
       
$line=explode("\n",preg_replace('/[^A-Za-z0-9\-+\n :;=%*?.,\/_]/','',substr($input,0,2000)));
       
// Split request line into its parts
       
list($client_header["method"],$client_header["url"],$client_header["protocol"])=explode(" ",$line[0]);
       
// Remove the request line again.
       
unset($line[0]);
       
// Make key=value array of headers
       
foreach($line as $l){
          list(
$key,$val)=explode(": ",$l);
          if(
$key) $client_header[strtolower($key)]=$val;
        }
       
// Get IP of client
       
socket_getpeername($newsocket, $client_header['ip']);

       
// Decode url
       
$client_header+=(array)parse_url($client_header['url']);
       
parse_str($client_header['query'],$client_header['arg']);

       
print_r($client_header);

       
// Serve file
       
if(strpos($client_header['path'],".html") && file_exists(__DIR__.$client_header['path'])){
          echo
"Sending a HTML page to client\n";
         
socket_write($newsocket,"$client_header[protocol] 200 OK\r\n");   
         
socket_write($newsocket,"Content-type: text/html; charset=utf-8\r\n\r\n");
         
socket_write($newsocket,file_get_contents(__DIR__.$client_header['path'])."\r\n\r\n");
         
socket_close($newsocket);
        }elseif(
$client_header['path']=="/test"){
          echo
"Sending test HTML page to client\n";
         
socket_write($newsocket,"<!DOCTYPE HTML><html><head><html><body><h1>Its working!</h1>Have fun\r\n");
         
socket_write($newsocket,"<pre>Request header: ". print_r($client_header,true) . "</pre>\r\n");
         
socket_write($newsocket,"</body></html>\r\n\r\n");
         
socket_close($newsocket);
        }else{
          echo
"$client_header[protocol] 404 Not Found\r\n";
         
socket_write($newsocket,"$client_header[protocol] 404 Not Found\r\n\r\n");  
         
socket_close($newsocket);
        }
      }
    }
  }
 
socket_close($host_socket);
?>
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2
Richard Neill
14 years ago
It is probably a bad idea to watch an array of sockets for input with socket_select, and then socket_read() using PHP_NORMAL_READ.

Although this seems desirable, you can end up with a permanently blocked program, if someone sends you malformed input which is missing a trailing \n \r. Guess how I found that out.
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0
eidberger at jakota dot de
10 years ago
Just noticed that you have to loop socket_select () when using UDP to get all queued packets:

<?php
while (socket_select ($aRead, $aWrite, $aExcept, 1) > 0) {
    foreach (
$aReadUdp as $oSocket) {
       
$this->clientReadUdp ($oSocket);
    }
}
?>

That's important because every call of socket_select () on UDP brings you only one result. But there could be 10.000 results queued and if your turnarround time is to slow (server busy, other sleeps etc.), you'll never progress all results in near realtime.
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0
danny at dansheps dot com
10 years ago
Just to add to this.  Since the information contained in the notes is somewhat old.   It appears keys are being preserved now.

So, if you rely on knowing which keys need to be worked with and were like me and thought that it didnot preserve.  Well it does.
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1
julian dot haupt at gmx dot de
16 years ago
hello,
i just made a class which acts similiar to Perl's IO::Select in order to make socket selecting very easy

your script should look something like that:

<?php
$server
= new Server;
$client = new Client;

for (;;) {
  foreach (
$select->can_read(0) as $socket) {

    if (
$socket == $client->socket) {
     
// New Client Socket
     
$select->add(socket_accept($client->socket));
    }
    else {
     
//there's something to read on $socket
   
}
  }
}
?>

you should of course implement some routines to detect broken sockets and remove them from the select object.

you can also do output buffering and check in the main-loop for sockets that are ready to write

<?php
class select {
  var
$sockets;

  function
select($sockets) {

   
$this->sockets = array();

    foreach (
$sockets as $socket) {
     
$this->add($socket);
    }
  }

  function
add($add_socket) {
   
array_push($this->sockets,$add_socket);
  }

  function
remove($remove_socket) {
   
$sockets = array();

    foreach (
$this->sockets as $socket) {
      if(
$remove_socket != $socket)
       
$sockets[] = $socket;
    }

   
$this->sockets = $sockets;
  }

  function
can_read($timeout) {
   
$read = $this->sockets;
   
socket_select($read,$write = NULL,$except = NULL,$timeout);
    return
$read;
  }

  function
can_write($timeout) {
   
$write = $this->sockets;
   
socket_select($read = NULL,$write,$except = NULL,$timeout);
    return
$write;
  }
}
?>
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0
Anonymous
12 years ago
If you want to use a simple fractional value for timeout:

<?php
socket_select
(..., floor($timeout), ceil($timeout*1000000));
?>
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0
Whosawhatsis at that google email thingy
13 years ago
Another solution to the problem of keys not being preserved is to have an additional array for looking up sockets that uses their resource identifiers as keys. This can be obtained using array_flip() in some cases, but is particularly useful if each socket is associated with an object. In this case, you can make the object's constructor add a pointer to itself to the lookup array with its socket resource identifier as a key and use the following code to execute a read method for the object associated with each socket returned by socket_select():

<?php
socket_select
($reads, $writes, $excepts, 0);

foreach (
$sockets as $socket) {
   
$lookuparray[$socket]->read();
}
?>
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0
ludvig dot ericson at gmail dot com
13 years ago
Regarding the comment below, No, it does not, it's a system call and I believe it's rather hard to preserve keys.

Additionally, socket_select should be used like it was a user-inputted array, that you don't know what you sent in to.

<?php
$reads
= $clients;
$reads[] = $server;

socket_select($reads);

foreach (
$reads as $read) {
   
/* do some stuff */
}
?>
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0
crimson at NOSPAMtechnologist dot com
13 years ago
Note that the resulting arrays do NOT maintain keys (PHP 4.3.2) after being run through this function:

Before:
Array
(
    [Client_Socket] => Resource id #6
    [Server_Socket] => Resource id #9
)

After:
Array
(
    [0] => Resource id #6
    [1] => Resource id #9
)

It would have been nice to have the keys stay to figure out which stream you need to receive from, but you'll have to use some fancy foreach loop to figure out which sockets to check.
up
-1
drenintell
14 years ago
The continuation of my my previous post on 28-Apr-2005 10:19 at
http://ca3.php.net/manual/en/function.socket-select.php

Here it is: (Link is broken into 2 parts)

'http://gtkphp.org/php_socket_select_hangs
_explanation_and_solution.html'
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-3
daveb at optusnet dot com dot au
16 years ago
If you haven't done any network programming before, PHP's socket_select() might appear a bit strange to you. I've written a simple php "partyline" script to demonstrate the multi-socket use of select'ing at http://dave.dapond.com/socketselect.php.txt
up
-9
Aaron (aaron at acephalo dot us)
9 years ago
socket_select() can also serve as a more granular sleep():

<?php
 
# half-second sleep
 
$undef = array();
 
socket_select($undef, $undef, $undef, 0, "500000");
?>
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