PHP: array_uintersect() unexpected input params [duplicate]

Question

Recently came across function array_uintersect. Just wondering if any one can explain how input params are passed as I got the unexpected inputs passed to callback function, I have already went through This answer but couldn't find answer to my question. Any help or leads will be appreciated, Just trying to understand working of call back function.

NOTE: RESULT OF FUNCTION IS PERFECTLY FINE.

Code:

function myfunction($a,$b) {
    echo "$a -- $b \n";
    if ($a===$b) {
        return 0;
    }
    return ($a>$b)?1:-1;
}

$a1 = array(1,2,3);
$a2 = array(4,5,1);
$result = array_uintersect($a1,$a2,"myfunction");
print_r($result);

As we are passing both the arrays as parameters,expected the inputs to be values from each array where as got below result.

Result:

1 -- 2
2 -- 3
4 -- 5
5 -- 1
4 -- 1
1 -- 1
1 -- 2
2 -- 4
3 -- 4
Array ( [0] => 1 )

Without looking at the PHP code, I would say there are two sets of results, the first one from where it is sorting $a1 and $a2 (up to 4 -- 1) and the second from where it is comparing them. But that is exactly what was said in the linked question, so what is your question? — Nick
– Nick, Commented Mar 6, 2019 at 5:35

dWinder · Accepted Answer · 2019-03-06 09:34:16Z

1

As @Nick mention in his comment (and also the link you shared) claim that array_uintersect sort the arrays before checking for intersect.

This will be the part of:

1 -- 2 // sort first array
2 -- 3 // sort first array
4 -- 5 // sort second array
5 -- 1 // sort second array
4 -- 1 // sort second array

Now both array are: $a1 = [1,2,3] and $a2 = [1,4,5].

Now the intersection part:

1 -- 1  // checking index 0 in both array
1 -- 2  // checking $a2[0] and $a1[1] -> 2 is bigger so let continue with him
2 -- 4  // checking $a1[1] and $a2[1] -> as we already check $a2[0] -> 4 is bigger so continue with him
3 -- 4  // checking $a1[2] and $a2[1] -> 4 is bigger but not $a1[3] so done checking

Notice the intersection can be done in O(n)because of the sort that done before...

edited Mar 6, 2019 at 9:34

answered Mar 6, 2019 at 8:51

dWinder

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