ActivityFeed.php

<?

include_once 'iredis.php';

class ActivityFeed {

	private $redis;
	
	public function __construct(){
		$this->redis = new iRedis();
	}
	
	// Adds an activity for a user
	public function add($userID, $data, $time = null){
		if(!$time) $time = time();
		$key = $this->_key('User', $userID);
		
		return $this->redis->zadd($key, $time, $data);
	}
	
	// Returns an array of the activity feed for userID
	public function userActivity($userID, $num = null, $before = null, $after = null){
		$key = $this->_key('User', $userID);
		
		$activity = $this->_activity($key, $num, $before, $after);
		
		return $activity;
	}
	
	// Returns an array of the union of activity feeds for the supplied userIDs
	// and stores it in a key for userID
	public function usersActivity($userID, $userIDs, $num = null, $before = null, $after = null){
		$usersKey = $this->_key('Users', $userID);
		
		$args = array();
		foreach($userIDs as $_userID){
			$args[] = $this->_key('User', $_userID);
		}
		
		// zunionstore expects parameters: destination numkeys key [key ...]
		array_unshift($args, $usersKey, count($userIDs));	
		call_user_func_array(array($this->redis, 'zunionstore'), $args);
		
		$usersActivity = $this->_activity($usersKey, $num, $before, $after);
		
		return $usersActivity;
	}
	
	// Helper method that returns an array of activity indexed by the activity time
	private function _activity($key, $num = null, $before = null, $after = null){
		$_activity = $this->redis->zrevrangebyscore($key, ( $before ? $before : '+inf' ), ( $after ? $after : '-inf' ), 'WITHSCORES');
		
		$activity = array();
		foreach($_activity as $key => $val){
			// When 'WITHSCORES' is provided, zrevrangebyscore returns an array in the format: (activity1, score1, activity2, score2, ...)
			if($key % 2 == 0){
				$activity[$_activity[$key + 1]] = $val;
			}
		}

		if($num) $activity = array_slice($activity, 0, $num);
		
		return $activity;
	}
	
	// Helper method that returns a namespaced key
	private function _key($type, $id){
		return "AF:$type:$id";
	}
}

?>

Added a bugfix: $num wasn't being respected