# msg_receive

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

msg_receive — Receive a message from a message queue

### 说明

msg_receive ( resource `$queue` , int `$desiredmsgtype` , int `&$msgtype` , int `$maxsize` , mixed `&$message` [, bool `$unserialize` = `TRUE` [, int `$flags` = 0 [, int `&$errorcode` ]]] ) : bool

msg_receive() will receive the first message from the specified `queue` of the type specified by `desiredmsgtype`.

### 参数

`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 a 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.

`msgtype`

  The 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).

  Flag values for msg_receive
  `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 to `MSG_ENOMSG`.
  `MSG_EXCEPT` | Using this flag in combination with a `desiredmsgtype` greater than 0 will cause the function to receive the first message that is not equal to `desiredmsgtype`.
  `MSG_NOERROR` | If the message is longer than `maxsize`, setting this flag will truncate the message to `maxsize` and will not signal an error.

`errorcode`

  If the function fails, the optional `errorcode` will be set to the value of the system errno variable.

### 返回值

成功时返回 `TRUE`， 或者在失败时返回 `FALSE`。

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.

### 参见

- msg_remove_queue() - Destroy a message queue
- msg_send() - Send a message to 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