05c03-1.php

来自「介绍PHP5的给类型函数应用」· PHP 代码 · 共 74 行

<?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 '<p>Queue size is: ', queue_size($myqueue), '</p>';

// Peek at the front of the queue, it should be: Opal
echo '<p>Front of the queue is: ', queue_peek($myqueue), '</p>';

// Now rotate the queue, giving us: Dolphin Pelican Opal
queue_rotate($myqueue);

// Remove the front element, returning: Dolphin
echo '<p>Removed the element at the front of the queue: ', 
    queue_dequeue($myqueue), '</p>';

// Now destroy it, we are done.
queue_destroy($myqueue);
?>