akritiko

/**
 * Time Travel returns dates in the past or the future, to a specific format, based on a seed date.
 * 
 * @param $date_format the format of dates (seed and returned)
 * @param $date the seed date
 * @param $where_to time travel "step" in days (e.g. for yesterday "-1", tomorrow "+1" and so forth) 
 */  
function time_travel( $date_format, $date, $where_to ) {
	return date( $date_format, strtotime( $date . ' ' . $where_to . ' day' ) );
}

akritiko

/**
 * Point-in-polygon based on Jordan Curve Theorem
 * 
 * Checks whether a point with a specific lat, long coordinates is inside 
 * a polygon defined by a given set of points. You can find more information
 * about the Jordan Curve Theorem to: 
 * http://en.wikipedia.org/wiki/Jordan_curve_theorem
 * 
 * The algorithm, originally implemented in c/c++ and can be found to   
 * http://sidvind.com/wiki/Point-in-polygon:_Jordan_Curve_Theorem.