function xorf($m, $n){

	$mid = $m % 2 == 0 ? $m/2 : ($m-1)/2;

	for($left = 0; $left <= $mid; $left++){

		$right = $m - $left ;

		$re = $left ^ $right;
		if ($re == $n){
			echo $left . ',' . $right . "<br>";
		}
	}
}

$m = 5;
$n = 1;

$m = 36;
$n = 26;

xorf($m, $n);