# imap_uid

(PHP 4, PHP 5, PHP 7, PHP 8)

imap_uid — This function returns the UID for the given message sequence number

### 说明

imap_uid(IMAP\Connection `$imap`, int `$message_num`): int|false

This function returns the UID for the given message sequence number. An UID is a unique identifier that will not change over time while a message sequence number may change whenever the content of the mailbox changes.

This function is the inverse of imap_msgno().

### 参数

`imap`

  IMAP\Connection 实例。

`message_num`

  The message number.

### 返回值

The UID of the given message.

### 更新日志

版本 | 说明
--- | ---
8.1.0 | 现在 `imap` 参数接受 IMAP\Connection 实例，之前接受有效的 `imap` resource。

### 注释

> 注意:

> This function is not supported by POP3 mailboxes.

### 参见

- imap_msgno() - Gets the message sequence number for the given UID

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