(PHP 4 >= 4.3.0, PHP 5)
msg_receive — Receive a message from a message queue
$queue
   , int $desiredmsgtype
   , int &$msgtype
   , int $maxsize
   , mixed &$message
   [, bool $unserialize = true
   [, int $flags = 0
   [, int &$errorcode
  ]]] )
   msg_receive() will receive the first message from the
   specified queue of the type specified by
   desiredmsgtype.
  
queue
desiredmsgtype
       If desiredmsgtype is 0, the message from the front
       of the queue is returned. If desiredmsgtype is
       greater than 0, then the first message of that type is returned.
       If desiredmsgtype is less than 0, the first
       message on the queue with the lowest type less than or equal to the
       absolute value of desiredmsgtype will be read.
       If no messages match the criteria, your script will wait until a suitable
       message arrives on the queue.  You can prevent the script from blocking
       by specifying MSG_IPC_NOWAIT in the
       flags parameter.
      
msgtypeThe type of the message that was received will be stored in this parameter.
maxsize
       The maximum size of message to be accepted is specified by the
       maxsize; if the message in the queue is larger
       than this size the function will fail (unless you set
       flags as described below).
      
message
       The received message will be stored in message,
       unless there were errors receiving the message.
      
unserialize
       If set to
       TRUE, the message is treated as though it was serialized using the
       same mechanism as the session module. The message will be unserialized
       and then returned to your script. This allows you to easily receive
       arrays or complex object structures from other PHP scripts, or if you
       are using the WDDX serializer, from any WDDX compatible source.
      
       If unserialize is FALSE, the message will be
       returned as a binary-safe string.
      
flags
       The optional flags allows you to pass flags to the
       low-level msgrcv system call.  It defaults to 0, but you may specify one
       or more of the following values (by adding or ORing them together).
       
| MSG_IPC_NOWAIT | If there are no messages of the desiredmsgtype, return immediately and do not
            wait.  The function will fail and return an integer value
            corresponding toMSG_ENOMSG. | 
| MSG_EXCEPT | Using this flag in combination with a desiredmsgtypegreater than 0 will cause the
            function to receive the first message that is not equal todesiredmsgtype. | 
| MSG_NOERROR | If the message is longer than maxsize,
            setting this flag will truncate the message tomaxsizeand will not signal an error. | 
errorcode
       If the function fails, the optional errorcode
       will be set to the value of the system errno variable.
      
   Returns TRUE on success or FALSE on failure.
  
Upon successful completion the message queue data structure is updated as follows: msg_lrpid is set to the process-ID of the calling process, msg_qnum is decremented by 1 and msg_rtime is set to the current time.