Socket Programming from PHP

Turned around, the same loop is a server. The listening socket becomes readable when a client is waiting, and stream_socket_accept() returns that client's stream:

echo-server.php: one process serving many TCP clientsPHP

<?php
$server = stream_socket_server('tcp://127.0.0.1:8223');
$clients = [];
while (true) {
  $read = $clients + ['listen' => $server];
  stream_select($read, $write, $except, null);  // sleep until something happens
  foreach ($read as $id => $sock) {
    if ($id === 'listen') {                     // a new client is waiting
      $c = stream_socket_accept($server);
      $clients[(int) $c] = $c;
    } elseif (($line = fgets($sock)) === false) {   // the peer hung up
      echo "client $id left\n";
      fclose($sock);                            // close now, or the peer waits for our FIN
      unset($clients[$id]);
    } else {
      echo "client $id said: $line";
      fwrite($sock, strtoupper($line));
    }
  }
}

Two nc clients connected at once, the second sending between the first one's two lines. Each got its own lines back in uppercase, and the server logged:

Output of 253

client 6 said: first line
client 7 said: second client
client 7 left
client 6 said: bye
client 6 left

ext/sockets mirrors the C API for UDP and raw options; stream sockets are simpler and speak TLS. Beware fgets() on a blocking socket: half a line from one client stalls all the others.

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Socket Programming from PHP