Reputation: 53607

Opposite of array_intersect?

Is there a built-in function to get all members of array 1 which do not exist in array 2?
I know how to do it programatically, only wondering if there is a built-in function that does the same. So please, no code examples.

Upvotes: 67

Answers (4)

Khel_MVA

Reputation: 48

Just to clarify as I was looking into this question the answers of @Jon and @Dallas Caley are both correct depending on the domain of your arrays.

If the array against what you are comparing is the full domain of your results then a simple array_diff will suffice as per @Jon answer.

If the array against what you are comparing is NOT the full domain of your results then you should go with the double array_diff as per @Dallas Caley answer.

Upvotes: 2

Dallas Caley

Reputation: 5878

array_diff is definitely the obvious choice but it is not technically the opposite of array interesect. Take this example:

$arr1 = array('rabbit','cat','dog');

$arr2 = array('cat','dog','bird');

print_r( array_diff($arr1, $arr2) );

What you want is a result with 'rabbit' and 'bird' in it but what you get is only rabbit because it is looking for what is in the first array but not the second (and not vice versa). to truly get the result you want you must do something like this:

$arr1 = array('rabbit','cat','dog');

$arr2 = array('cat','dog','bird');

$diff1 = array_diff($arr1, $arr2);
$diff2 = array_diff($arr2, $arr1);
print_r( array_merge($diff1, $diff2) );