(PECL sam >= 0.1.0)
SAMConnection::subscribe — Create a subscription to a specified topic.
$targetTopic
   )The "subscribe" method is used to create a new subscription to a specified topic.
targetTopicThe identity of the topic (topic://topicname) to subscribe to.
   A subscription identifier that can be used in a subsequent receive call as
   a selector to obtain any topic data or FALSE if an error occurred. The
   subscription identifier should be used in the receive call in place of the
   simple topic name.
  
Example #1 Subscribe to a topic
<?php
$subid = $conn->subscribe('topic://A');
if (!$subid) {
  // The subscribe failed!
  echo "Subscribe failed ($conn->errno) $conn->error";
}
?>