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   1 # pq\Connection: Asynchronous Usage
   2
   3 Whenever you start an asynchronous operation, you will have to probe pq\Connection::poll() to determine the current status of the operation.
   4
   5 You can then use the ***public readonly*** property pq\Connection::$socket with ```stream_select()``` to wait for read/write-readiness.
   6
   7 > ***NOTE:***
   8 You cannot use the connection for anything else while an asynchronous operation is active.
   9
  10 ## Connect or reset asynchronously:
  11
  12 First, you can establish or reset a connection asynchronously.
  13
  14 ### Start asynchronous connect:
  15
  16         <?php
  17
  18         $c = new pq\Connection(null, pq\Connection::ASYNC);
  19
  20         ?>
  21
  22 ### Start asynchronous reset:
  23
  24         <?php
  25
  26         $c->resetAsync();
  27
  28         ?>
  29
  30 ### Complete asynchronous operation:
  31
  32 Keep in mind that you have to test for write-readiness once *before* starting the polling loop on connect/reset.
  33
  34         <?php
  35
  36         // wait until the stream becomes writable
  37         $w = array($c->socket);
  38         $r = $e = null;
  39
  40         if (stream_select($r, $w, $e, null)) {
  41
  42           // loop until the connection is established
  43           while (true) {
  44
  45                 switch ($c->poll()) {
  46
  47                 case pq\Connection::POLLING_READING:
  48                   // we should wait for the stream to be read-ready
  49                   $r = array($c->socket);
  50                   stream_select($r, $w, $e, NULL);
  51                   break;
  52
  53                 case pq\Connection::POLLING_WRITING:
  54                   // we should wait for the stream to be write-ready
  55                   $w = array($c->socket);
  56                   $r = $e = null;
  57                   stream_select($r, $w, $e, null);
  58                   break;
  59
  60                 case pq\Connection::POLLING_FAILED:
  61                   printf("Connection failed: %s\n", $c->errorMessage);
  62                   break 2;
  63
  64                 case pq\Connection::POLLING_OK:
  65                   printf("Connection completed\n");
  66                   break 2;
  67                 }
  68         }
  69
  70         ?>
  71
  72
  73 If you use an appropriate timeout in the ```stream_select()``` call and do something else at the end of the while loop, you probably got the idea...
  74
  75 ## Execute queries asynchronously:
  76
  77         <?php
  78
  79         $c = new pq\Connection;
  80         $c->execAsync("SELECT 1+2+3; SELECT 2,3,4", function ($res) {
  81           var_dump($res);
  82         });
  83
  84         ?>
  85
  86 The body of the while loop looks slightly different, when executing queries asynchronously, because you only have to wait for read-readiness.
  87
  88 You can use the ***public readonly*** property pq\Connection::$busy to test if a call to pq\Connection::getResult() would block, and if so wait for read-readiness and then call pq\Connection::poll().
  89
  90         <?php
  91
  92         do {
  93           while ($c->busy) {
  94                 $r = array($c->socket);
  95                 $w = $e = null;
  96                 if (stream_select($r, $w, $e, null)) {
  97                   $c->poll();
  98                 }
  99           }
 100         } while ($c->getResult());
 101
 102         ?>
 103
 104 If pq\Connection::getResult() returns NULL, there's nothing more in the pipeline.