PHP删除数组中的特定的一个值用array_diff函数

$a1=array("Cat","Dog","Horse",'dff','dfdf','www');
$a2=array("dff","Horse","Dog");
$a1 = array_diff($a1,$a2);
sort($a1);
print_r($a1);

Array
(
    [0] => Cat
    [1] => dfdf
    [2] => www
)