msg_send() sends a message of type msgtype (which MUST be greater than 0) to a the message queue specified by queue.
If the message is too large to fit in the queue, your script will wait until another process reads messages from the queue and frees enough space for your message to be sent. This is called blocking; you can prevent blocking by setting the optional blocking parameter to FALSE, in which case msg_send() will immediately return FALSE if the message is too big for the queue, and set the optional errorcode to EAGAIN, indicating that you should try to send your message again a little later on.
The optional serialize controls how the message is sent. serialize defaults to TRUE which means that the message is serialized using the same mechanism as the session module before being sent to the queue. This allows complex arrays and objects to be sent to other PHP scripts, or if you are using the WDDX serializer, to any WDDX compatible client.
Upon successful completion the message queue data structure is updated as follows: msg_lspid is set to the process-ID of the calling process, msg_qnum is incremented by 1 and msg_stime is set to the current time.
This function was introduced in PHP 4.3.0 (not yet released).