PHP Array -- PHP实现队列 -- PHP Queues

 "队列"遵循先入先出(FIFO)原则，工作方式类似于剧场，先到者会先得到服务.

 

 

下面是一个提供全部队列常用操作的函数库。

 

// 来自 PHP5 in Practice  (U.S.)Elliott III & Jonathan D.Eisenhamer

 

 

<?php// A library to implement queues in PHP via arrays// The Initialize function creates a new queue:function &queue_initialize() { // In this case, just return a new array $new = array(); return $new;}// The destroy function will get rid of a queuefunction queue_destroy(&$queue) { // Since PHP is nice to us, we can just use unset unset($queue);}// The enqueue operation adds a new value unto the back of the queuefunction queue_enqueue(&$queue, $value) { // We are just adding a value to the end of the array, so can use the // [] PHP Shortcut for this. It's faster than using array_push $queue[] = $value;}// Dequeue removes the front of the queue and returns it to youfunction queue_dequeue(&$queue) { // Just use array unshift return array_shift($queue);}// Peek returns a copy of the front of the queue, leaving it in placefunction queue_peek(&$queue) { // Return a copy of the value found in front of queue // (at the beginning of the array) return $queue[0];}// Size returns the number of elements in the queuefunction queue_size(&$queue) { // Just using count will give the proper number: return count($queue);}// Rotate takes the item on the front and sends it to the back of the queue.function queue_rotate(&$queue) { // Remove the first item and insert it at the rear. $queue[] = array_shift($queue);}// Let's use these to create a small queue of data and manipulate it.// Start by adding a few words to it:$myqueue =& queue_initialize();queue_enqueue($myqueue, 'Opal');queue_enqueue($myqueue, 'Dolphin');queue_enqueue($myqueue, 'Pelican');// The queue is: Opal Dolphin Pelican// Check the size, it should be 3echo '<p>Queue size is: ', queue_size($myqueue), '</p>';// Peek at the front of the queue, it should be: Opalecho '<p>Front of the queue is: ', queue_peek($myqueue), '</p>';// Now rotate the queue, giving us: Dolphin Pelican Opalqueue_rotate($myqueue);// Remove the front element, returning: Dolphinecho '<p>Removed the element at the front of the queue: ', queue_dequeue($myqueue), '</p>';// Now destroy it, we are done.queue_destroy($myqueue);?>