(PECL ds >= 1.0.0)
Ds\Queue::peek — Returns the value at the front of the queue
Returns the value at the front of the queue, but does not remove it.
此函数没有参数。
The value at the front of the queue.
UnderflowException if empty.
示例 #1 Ds\Queue::peek() example
<?php
$queue = new \Ds\Queue();
$queue->push("a");
$queue->push("b");
$queue->push("c");
var_dump($queue->peek());
?>以上示例的输出类似于：
string(1) "a"