Sometimes you need a list of the dates between two dates.

    /**
     * Returns an array with the dates between to dates given.
     *
     * @link http://us3.php.net/manual/en/function.date.php#AEN25217
     * 
     * @param mixed $startdate Timestamp or strtotime() recognizeable string
     * @param mixed $enddate Timestamp or strtotime() recognizeable string
     * @param string[optional] $format date() format string
     * @return mixed Array of timestamps or dates if given format
     */
    public static function dates_between($startdate, $enddate, $format=null){
 
        (is_int($startdate)) ? 1 : $startdate = strtotime($startdate);
        (is_int($enddate)) ? 1 : $enddate = strtotime($enddate);
 
        if($startdate > $enddate){
            return false; //The end date is before start date
        }
 
        while($startdate < $enddate){
            $arr[] = ($format) ? date($format, $startdate) : $startdate;
            $startdate += 86400;
        }
        $arr[] = ($format) ? date($format, $enddate) : $enddate;
 
        return $arr;
    }

You can give it a timestamp or a string date. It will use date() to format the output if given a $format.