The SplHeap class

To have a good idea what you can do with SplHeap, I created a little example script that will show the rankings of Belgian soccer teams in the Jupiler League.<?php/** * A class that extends SplHeap for showing rankings in the Belgian * soccer tournament JupilerLeague */class JupilerLeague extends SplHeap {    /**     * We modify the abstract method compare so we can sort our     * rankings using the values of a given array     */    public function compare($array1, $array2)    {        $values1 = array_values($array1);        $values2 = array_values($array2);        if ($values1[0] === $values2[0]) return 0;        return $values1[0] < $values2[0] ? -1 : 1;    }}// Let's populate our heap here (data of 2009)$heap = new JupilerLeague();$heap->insert(array ('AA Gent' => 15));$heap->insert(array ('Anderlecht' => 20));$heap->insert(array ('Cercle Brugge' => 11));$heap->insert(array ('Charleroi' => 12));$heap->insert(array ('Club Brugge' => 21));$heap->insert(array ('G. Beerschot' => 15));$heap->insert(array ('Kortrijk' => 10));$heap->insert(array ('KV Mechelen' => 18));$heap->insert(array ('Lokeren' => 10));$heap->insert(array ('Moeskroen' => 7));$heap->insert(array ('Racing Genk' => 11));$heap->insert(array ('Roeselare' => 6));$heap->insert(array ('Standard' => 20));$heap->insert(array ('STVV' => 17));$heap->insert(array ('Westerlo' => 10));$heap->insert(array ('Zulte Waregem' => 15));// For displaying the ranking we move up to the first node$heap->top();// Then we iterate through each node for displaying the resultwhile ($heap->valid()) {  list ($team, $score) = each ($heap->current());  echo $team . ': ' . $score . PHP_EOL;  $heap->next();}?>This results in the following output:Club Brugge: 21Anderlecht: 20Standard: 20KV Mechelen: 18STVV: 17Zulte Waregem: 15AA Gent: 15G. Beerschot: 15Charleroi: 12Racing Genk: 11Cercle Brugge: 11Kortrijk: 10Lokeren: 10Westerlo: 10Moeskroen: 7Roeselare: 6Hope this example paved the way for more complex implementations of SplHeap.

While Michelangelo Van Dam example (http://br2.php.net/manual/en/class.splheap.php#93930) is a great demonstration of what can be done with SplHeap, this implementation is exactly what SplPriorityQueue does - based on SplMaxHeap. If you're planning to copy that snippet, go no further! There's a SPL class that does exactly what you want :)

If you wish to build a true tree based heap, you can do so as follows (implemented with SplMinHeap, but could be SplMaxHeap if you wish for the opposite order of items):The stucture that we're trying to represent:         1         |+-----+--+--+-----+|     |     |     |2     3     4     5|     |           |+   +-+-+         +|   |   |         |7   6   8         9                  |                +-+-+                |   |               10   11<?php$h = new SplMinHeap();// [parent, child]$h->insert([9, 11]);$h->insert([0, 1]);$h->insert([1, 2]);$h->insert([1, 3]);$h->insert([1, 4]);$h->insert([1, 5]);$h->insert([3, 6]);$h->insert([2, 7]);$h->insert([3, 8]);$h->insert([5, 9]);$h->insert([9, 10]);for ($h->top(); $h->valid(); $h->next()) {    list($parentId, $myId) = $h->current();    echo "$myId ($parentId)\n";}?>As you iterate over the heap, the return data will be read as if you're reading a book; ie left to right, top to bottom. It will NOT follow the relationships.So, the above code will output the following:1 (0)2 (1)3 (1)4 (1)5 (1)7 (2)6 (3)8 (3)9 (5)10 (9)11 (9)