Checks / verify if 2 points are adjacent in a 2 dimension space

space.neighbours.php

/** Calculates, from two set of coord, if two nodes are adjacents.
	 * @return bool|null True if they are adiacents, null if the coords are not valid or are the same.
	 */
	 public static function areNodeAdjacents($coord_1_norm,$coord_2_norm)
	 {
		
 		if ($coord_1_norm['x'] === $coord_2_norm['x'] AND $coord_1_norm['y'] === $coord_2_norm['y'])//or is the same planet ..
 			return null;
 			
		//the formula
		if (max(abs($coord_1_norm['x']-$coord_2_norm['x']),abs($coord_1_norm['y']-$coord_2_norm['y'])) <= 1)
		{
			return true;
		}
		else
		{
			return false;
		}
	 }