array_diff not returning what's expected

Question

I've read some tutorials on here but none of them return what I need. I have two arrays. ``` $arrayA = array(1960,1961,1963,1962,1954,1953,1957,1956,1955); $arrayB = array(1949,1960,1961,1963,1962,1954,1953,1957,1956,1955); ``` However, when I run array_diff, it returns an empty array. ``` $diff = array_diff($arrayA, $arrayB); ``` But I'd like it to return 1949. What's the error in my code? edit: since switching the variables won't work, i did var_dump for the 3 arrays (A, B, and diff) and here's the pastebin http://pastebin.com/tn1dvCs3

Accepted Answer

`array_diff` works by finding the elements in the first array that aren't in the second, per the documentation. Try inverting your call:

```
$diff = array_diff($arrayB, $arrayA);
```

To see this in action, lets look at a more manageable but equivalent example:

```
$arrayA = array(1960);
$arrayB = array(1949,1960);

$diff = array_diff($arrayB, $arrayA);
var_dump($diff);
```

This yields:

```
[mylogin@aserver ~]$ vim test.php
[mylogin@aserver ~]$ php test.php
array(1) {
  [0]=>
  int(1949)
}
```

Please note that this uses a minimal demonstrative example of the functionality you're attempting to get. By discarding unnecessary data in your actual implementation you can more quickly zero in on the problem you're having.

array_diff not returning what's expected

Solution

Problem