Made SplPriorityQueue honor insert order for equal priorities

- Overwrote insert() method to enforce FIFO order for values of the same
  priority
- Zend\Stdlib\PriorityQueue now utilizes Zend\Stdlib\SplPriorityQueue
  internally
- Zend\SignalSlot\Filter\FilterIterator now utilizes
  Zend\Stdlib\SplPriorityQueue internally

src/PriorityQueue.php

@@ -54,7 +54,7 @@ class PriorityQueue implements Countable, IteratorAggregate, Serializable
      * Inner queue class to use for iteration
      * @var string
      */
-    protected $queueClass = 'SplPriorityQueue';
+    protected $queueClass = 'Zend\Stdlib\SplPriorityQueue';
 
     /**
      * Actual items aggregated in the priority queue. Each item is an array

src/SplPriorityQueue.php

@@ -28,13 +28,39 @@
 /**
  * Serializable version of SplPriorityQueue
  *
+ * Also, provides predictable heap order for datums added with the same priority
+ * (i.e., they will be emitted in the same order they are enqueued).
+ *
  * @category   Zend
  * @package    Zend_Stdlib
  * @copyright  Copyright (c) 2005-2010 Zend Technologies USA Inc. (http://www.zend.com)
  * @license    http://framework.zend.com/license/new-bsd     New BSD License
  */
 class SplPriorityQueue extends \SplPriorityQueue implements Serializable
 {
+    /**
+     * @var int Seed used to ensure queue order for items of the same priority
+     */
+    protected $serial = PHP_INT_MAX;
+
+    /**
+     * Insert a value with a given priority
+     *
+     * Utilizes {@var $serial} to ensure that values of equal priority are 
+     * emitted in the same order in which they are inserted.
+     * 
+     * @param  mixed $datum 
+     * @param  mixed $priority 
+     * @return void
+     */
+    public function insert($datum, $priority)
+    {
+        if (!is_array($priority)) {
+            $priority = array($priority, $this->serial--);
+        }
+        parent::insert($datum, $priority);
+    }
+
     /**
      * Serialize to an array
      *
@@ -60,7 +86,7 @@ public function toArray()
         // Return only the data
         $return = array();
         foreach ($array as $item) {
-            $return[$item['priority']] = $item['data'];
+            $return[] = $item['data'];
         }
 
         return $return;

test/SplPriorityQueueTest.php

@@ -43,6 +43,22 @@ public function setUp()
         $this->queue->insert('bat', 1);
     }
 
+    public function testMaintainsInsertOrderForDataOfEqualPriority()
+    {
+        $queue = new SplPriorityQueue();
+        $queue->insert('foo', 1000);
+        $queue->insert('bar', 1000);
+        $queue->insert('baz', 1000);
+        $queue->insert('bat', 1000);
+
+        $expected = array('foo', 'bar', 'baz', 'bat');
+        $test     = array();
+        foreach ($queue as $datum) {
+            $test[] = $datum;
+        }
+        $this->assertEquals($expected, $test);
+    }
+
     public function testSerializationAndDeserializationShouldMaintainState()
     {
         $s = serialize($this->queue);
@@ -64,10 +80,10 @@ public function testSerializationAndDeserializationShouldMaintainState()
     public function testCanRetrieveQueueAsArray()
     {
         $expected = array(
-            4 => 'bar', 
-            3 => 'foo', 
-            2 => 'baz', 
-            1 => 'bat',
+            'bar', 
+            'foo', 
+            'baz', 
+            'bat',
         );
         $test     = $this->queue->toArray();
         $this->assertSame($expected, $test, var_export($test, 1));