msg_send
(PHP 4 >= 4.3.0, PHP 5)
msg_send — Send a message to a message queue
Description
$queue
, int $msgtype
, mixed $message
[, bool $serialize = true
[, bool $blocking = true
[, int &$errorcode
]]] )
msg_send() sends a message of type
msgtype (which MUST be greater than 0) to
the message queue specified by queue.
Parameters
-
queue -
-
msgtype -
-
message -
-
serialize -
The optional
serializecontrols how themessageis sent.serializedefaults toTRUEwhich means that themessageis 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. -
blocking -
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
blockingparameter toFALSE, in which case msg_send() will immediately returnFALSEif the message is too big for the queue, and set the optionalerrorcodetoMSG_EAGAIN, indicating that you should try to send your message again a little later on. -
errorcode -
Return Values
Returns TRUE on success or FALSE on failure.
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.
See Also
- msg_remove_queue() - Destroy a message queue
- msg_receive() - Receive a message from a message queue
- msg_stat_queue() - Returns information from the message queue data structure
- msg_set_queue() - Set information in the message queue data structure
Коментарии
After about an hour of debugging I've discovered the meaning of the undocumented "PHP Warning: msg_send(): msgsnd failed: Invalid argument" ($errorcode = 13).
This occurred when the size of $message was larger than msg_qbytes (see msg_stat_queue() for how to determine and change msg_qbytes).
When sending non-complex (serialize = false) messages to a program in C, you need to add the null character to the string (\0). Otherwise the previous message will be partially visible if it is longer than the current message. Took some kind help from comp.lang.php for me to figure that out. While it seems so obvious now, I thought I'd share it here.I created example how to comunnicate with programe written in C throught messages queues. First run C program (it will create queue) then PHP script.
C code compile with: gcc -std=c99 -o test_queue test_queue.c
test_queue.c:
/**
* Example how to use System V Messages Queues with PHP and C program.
* This is simple server which create message queue and receive message from it.
* Based on Beej's Guide to Unix IPC
* Autor: Jan Drazil, <qeekin at gmail dot com>
*/
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/msg.h>
/* Buffer struct for receiving messages */
struct php_buf {
long mtype;
char msg[200];
};
int main(void)
{
struct php_buf buf;
int msqid;
key_t key;
/* Generate key (/var/www/index.php must be accessible file) */
if((key = ftok("/var/www/index.php", 'G')) == -1) {
perror("ftok");
exit(EXIT_FAILURE);
}
/* Create message queue */
if((msqid = msgget(key, 0666 | IPC_CREAT)) == -1) {
perror("msgget");
exit(EXIT_FAILURE);
}
printf("Ready to get string from PHP!\n");
/* Receive message */
if(msgrcv(msqid, &buf, sizeof(buf.msg)-1, 0, 0) == -1) {
perror("msgrcv");
exit(EXIT_FAILURE);
}
/* Eliminate segmentation fault */
buf.msg[199] = '\0';
printf("Recieved from PHP: %s\n", buf.msg);
/* Destroy message queue */
if(msgctl(msqid, IPC_RMID, NULL) == -1) {
perror("msgctl");
exit(EXIT_FAILURE);
}
return EXIT_SUCCESS;
}
test_queue.php:
<?php
/**
* Example how to use System V Messages Queues with PHP and C program.
* This is simple server which create message queue and receive message from it.
* Based on Beej's Guide to Unix IPC
* Autor: Jan Drazil, <qeekin at gmail dot com>
*/
/* Generate key, param fot ftok must be same as in test_msg.c */
if(($key = ftok("/var/www/index.php", "G")) == -1)
die("ftok");
if(!msg_queue_exists($key))
die("message queue doesn't exists");
/* Connect to message queue */
if(($msqid = msg_get_queue($key)) === FALSE)
die("msg_get_queue");
echo "Sending text to msg queue.\n";
/* Send message to C program */
if(!msg_send($msqid, 12, "Hello from PHP!\0", false))
die("msg_send");
echo "Done"
?>