(PECL event >= 1.2.6-beta)
EventBuffer::freeze — Prevent calls that modify an event buffer from succeeding
$at_front
): boolPrevent calls that modify an event buffer from succeeding
at_front
Whether to disable changes to the front or end of the buffer.
成功時(shí)返回 true， 或者在失敗時(shí)返回 false。