PHP Array -- PHP实现队列 -- PHP Queues

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本文介绍了一种使用PHP实现队列数据结构的方法，并提供了包括初始化、销毁、入队、出队等基本操作在内的完整函数库。通过示例展示了如何创建和操作队列。

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"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 $new; } // The destroy function will get rid of a queue function queue_destroy(&$queue) { // Since PHP is nice to us, we can just use unset unset($queue); } // The enqueue operation adds a new value unto the back of the queue function queue_enqueue(&$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[] = $value; } // Dequeue removes the front of the queue and returns it to you function queue_dequeue(&$queue) { // Just use array unshift return array_shift($queue); } // Peek returns a copy of the front of the queue, leaving it in place function queue_peek(&$queue) { // Return a copy of the value found in front of queue // (at the beginning of the array) return $queue[0]; } // Size returns the number of elements in the queue function queue_size(&$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 3 echo 'Queue size is: ', queue_size($myqueue), ''; // Peek at the front of the queue, it should be: Opal echo 'Front of the queue is: ', queue_peek($myqueue), ''; // Now rotate the queue, giving us: Dolphin Pelican Opal queue_rotate($myqueue); // Remove the front element, returning: Dolphin echo 'Removed the element at the front of the queue: ', queue_dequeue($myqueue), ''; // Now destroy it, we are done. queue_destroy($myqueue); ?>