$array1 = array (
	[474] => 482,
	[496] => 208
);
$array2 = array (
	[474] => 474,
	[496] => 496,
	[496] => 496
);
$array3 = array();
foreach($array2 as $key => $val){
	$array3 = (isset($array1[$key]))?$array1[$key]):$val;
};

print_r($array3); // just show it :P