msg_send

(PHP 4 >= 4.3.0, PHP 5, PHP 7, PHP 8)

msg_send — Send a message to a message queue

Description

msg_send(
    SysvMessageQueue $queue,
    int $message_type,
    string|int|float|bool $message,
    bool $serialize = true,
    bool $blocking = true,
    int &$error_code = null
): bool

msg_send() sends a message of type message_type (which MUST be greater than 0) to the message queue specified by queue.

Parameters

queue: The message queue.
message_type: The type of the message (MUST be greater than 0)
message: The body of the message.

Note:
If serialize set to false is supplied, MUST be of type: string, int, float or bool. In other case a warning will be issued.
serialize: 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.
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 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 error_code to MSG_EAGAIN, indicating that you should try to send your message again a little later on.
error_code: If the function fails, the optional errorcode will be set to the value of the system errno variable.

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.

Changelog

Version	Description
8.0.0	`queue` expects a SysvMessageQueue instance now; previously, a resource was expected.

User Contributed Notes 6 notes

down

qeekin at gmail dot com ¶

10 years ago


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"
?>

down

Muffinman ¶

12 years ago


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.

down

shepik at yandex dot ru ¶

15 years ago


$msgtype used in msg_send function can be any positive integer.

down

michael dot NO dot SP dot AM dot cordover+php at gmail dot com ¶

15 years ago


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).

down

-1

bryan-boone at msn dot com ¶

16 years ago


I think it is kinda lame why I cannot find out (easily) explicitly which types of messages are allowed and which ones are not.  Maybe we can start our own little list.  I know that strings work, and arrays do not.

down

-2

webmaster at toolshed51 dot com ¶

21 years ago


Sample sending webpage, see msg_receive for matching service

<?php
    $MSGKEY = 519051;

    $msg_id = msg_get_queue ($MSGKEY, 0600);

    if (!msg_send ($msg_id, 1, 'Hi', true, true, $msg_err))
        echo "Msg not sent because $msg_err\n";
?>

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msg_send

Description

Parameters

Return Values

Changelog

See Also

User Contributed Notes 6 notes