array_diff_key:根据数组键计算多个数组的差集

1. [代码]array_diff_key    

$arr1 = array('a'=>'aa','b'=>'bb','c'=>'cc','d'=>'dd');
$arr2 = array('a'=>'aaa','b'=>'bbb','f'=>'fff');

$arr = array_diff_key($arr1,$arr2);

echo '<pre>';
print_r($arr);

result:
Array
(
    [c] => cc
    [d] => dd
)