I want to conditionally display ads based on other ads

Eric,

Thanks for the tip. I think I solved my problem. Maybe this is something you want to include in the trunk of this project as an option to turn on and off as users wish?

Basically I decided to use a static private array member of the DFADS class.

Each time an ad result is returned by the query, I grab its ID and put that in the array. When I perform the query I check and make sure the IDs of the results I’m pulling back are not in the array’s values.

This works great for guaranteeing that no ad is displayed more than once on a page.

Class DFADS() {
    private static $excluded_ads = array();

    function get_ads( $args ) {
        ...
        // Get ads.
        $ads = $this->query();

        ...
        foreach ($ads as $ad) {
            self::$excluded_ads[] = $ad->ID;
        }
    }
    ...
    function query() {
        ...
        $exclude_ads = $this->sql_get_excluded_ads();

        // SQL WHERE clause construction
        ...
        AND (
                p.ID NOT IN ($exclude_ads)
            )
        ...
    }
    ...
    function sql_get_excluded_ads() {
        if (empty(self::$excluded_ads)){
            return '-1';
        } else {
            return implode(',',self::$excluded_ads);
        }
    }
}

And that’s it basically. I’m also looking into adding functionality that would restrict a single advertiser’s ads from taking a majority of the ad spots if there are multiple advertisers and they should be sharing the available space.