agenticsim · October 23, 2013 08:22 · Oct 23, 2013
diff --git a/queue.php b/queue.php
@@ -0,0 +1,59 @@
+<?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);  
+?>