Creating a Banner Swapping Algorithm to Rotate Ads

Question

I\'m working on building an ad banner rotation script based on impressions that displays ads evenly throughout the month. The calculations will be done each time the ad

Answer 1

I think you should use the best type of algorithm for the best JOB i'll only show you some few possibility on how to implement such

My current example would show using

• shuffle
• fisherYatesShuffle
• robinShuffle
• ratioShuffle

You can also implement

• Priory Based shuffle
• Time Base Shuffle
• Percentage
• Click Shuffle
• etc

Simple Prove of Concept

// Create Add Infroamtion
$ads = array();
$ads[] = new Ad(10, "A.jpg", 2);
$ads[] = new Ad(12, "B.gif", 3);
$ads[] = new Ad(30, "C.png", 7);
$ads[] = new Ad(20, "D.swf", 5);

// Add ads to banner
$banner = new Banner($ads);

// You can also add addional ads
$banner->add(new Ad(10, "E.swf"));

echo "<pre>";

//Lets Emulate first 100 rotations 
for($i = 0; $i < 1000; $i ++) {
    // Select Algorithm
    $banner->randomise("ratioShuffle");

    // Display Add
    echo $banner->getDisplay(), PHP_EOL;
}

Simple Shuffle Function that can be used

function fisherYatesShuffle(array &$items) {
    for($i = count($items) - 1; $i > 0; $i --) {
        $j = @mt_rand(0, $i);
        $tmp = $items[$i];
        $items[$i] = $items[$j];
        $items[$j] = $tmp;
    }
}

function robinShuffle(array &$items) {
    usort($items, function ($a, $b) {
        $a = $a->getDisplay();
        $b = $b->getDisplay();
        return $a == $b ? 0 : ($a < $b ? - 1 : 1);
    });
}

function ratioShuffle(array &$items) {
    static $called = false;
    if ($called === false) {
        $ads = array();
        foreach ( $items as &$ad ) {
            for($i = 0; $i < $ad->getRatio(); $i ++) {
                $ads[] = $ad;
            }
        }
        $called = true;
        $items = $ads;
    }
    shuffle($items);
}

Classes Used

class Ad implements JsonSerializable {
    private $impressions;
    private $media;
    private $ratio = 1;
    private $display = 0;

    function __construct($impressions, $media = null, $ratio = 1) {
        $this->impressions = $impressions;
        $this->media = $media;
        $this->ratio = $ratio;
    }

    function torch() {
        $this->impressions --;
        $this->display ++;
    }

    public function getImpression() {
        return $this->impressions;
    }

    public function getDisplay() {
        return $this->display;
    }

    public function getRatio() {
        return $this->ratio;
    }

    public function getMeadia() {
        return $this->media;
    }

    public function __toString() {
        return json_encode($this->jsonSerialize());
    }

    public function jsonSerialize() {
        return get_object_vars($this);
    }
}


class Banner implements Countable, JsonSerializable {
    private $totalImpressions;
    private $ads = array();

    function __construct(array $ads) {
        foreach ( $ads as $ad )
            $this->add($ad);
    }

    public function add(Ad $ad) {
        $this->ads[] = $ad;
        $this->totalImpressions += $ad->getImpression();
    }

    public function randomise($function = null) {
        if (is_callable($function, false, $callable_name)) {
            return $callable_name($this->ads);
        } else {
            return shuffle($this->ads);
        }
    }

    public function getDisplay() {
        foreach ( $this->ads as &$ad ) {
            if ($ad->getImpression() < 1) {
                unset($ad);
                continue;
            }
            $ad->torch();
            break;
        }
        return isset($ad) ? $ad : null;
    }

    public function jsonSerialize() {
        $array = $this->ads;
        foreach ( $array as &$ad ) {
            $ad = $ad->jsonSerialize();
        }
        return $array;
    }

    public function __toString() {
        return json_encode($this->jsonSerialize());
    }

    function count() {
        return count($this->ads);
    }
}

As you can see this is an example .... Just try and make your solution flexible

Answer 2

Personally, I'd work out what percentage of impressions each ad has received compared to how many are paid for, and use that as the chance that it won't show up. Something like this:

$show = Array();
foreach($ads as $id=>$ad) {
    $show[$id] = ceil((1-$ad['impressions']/$ad['paid'])*100);
}
$total = array_sum($show);
$rand = rand(1,$total);
$winner = -1;
do {$rand -= array_shift($show); $winner++;} while($rand && $show);
$ad_to_display = $ads[$winner];

For example, consider four ads, A, B, C and D. All of them have paid for 1,000 impressions, but so far A has been unlucky and gotten zero, while B and C both have had 500 impressions, and D has had 999.

This would mean $show has these values for the ads:

A: ceil((1-0/1000)*100) = 100
B: ceil((1-500/1000)*100) = 50
C: ceil((1-500/1000)*100) = 50
D: ceil((1-999/1000)*100) = 1

$total is therefore equal to 201.

$rand can be any number from 1 to 201 inclusive. Let's say 141.

In this case, we begin our loop:

• $rand -= 100, now it's 41. 41 is truthy and we have ads remaining.
• $rand -= 50, now it's -9. It has reached zero, so end the loop.

The $winner is 1, which is advert B.