(PECL pht >= 0.0.1)
pht\Queue::front — Returns the first value from a queue
This method will remove a value from the front of the queue (in constant time). Attempting to return the front value from an empty queue will result in an Error exception.
Due to the fact that all values in a pht\Queue are serialised, extracting a value from the queue will require it to be deserialised. This can incur a noticeable performance hit if the inspection of the queue's front value is performed within a loop.
此函数没有参数。
The value on the front of the queue.
示例 #1 Retrieving the front value of a queue
<?php
use pht\Queue;
$queue = new Queue();
$queue->push(1);
var_dump($queue->front());
以上例程会输出：
int(1)
示例 #2 Retrieving the front value in a loop (bad example - don't do this)
<?php
use pht\Queue;
$queue = new Queue();
$queue->push(array_fill(0, 2000, 0));
for ($i = 0; $i < count($queue->front()); ++$i); // quadratic runtime
示例 #3 Retrieving the front value in a loop (good example)
<?php
use pht\Queue;
$queue = new Queue();
$queue->push(array_fill(0, 2000, 0));
$front = $queue->front(); // create a separate variable
for ($i = 0; $i < count($front); ++$i); // linear runtime