Intersect unknown number of arrays in PHP

Question

I'm trying to intersect an arbitrary number of PHP arrays, the count of which depends on a user provided parameter, each of which can have any number of elements.

For example: array1(1, 2, 3, 4, 5) array2(2, 4, 6, 8, 9, 23) array3(a, b, 3, c, f) ... arrayN(x1, x2, x3, x4, x5 ... xn)

Since array_intersect takes a list of params, I can't build one array of arrays to intersect and have to work my way around this. I tried this solution: http://bytes.com/topic/php/answers/13004-array_intersect-unknown-number-arrays but this did not work, as an error is reported that array_intersect requires 2 or more params.

Does anyone have any idea how to approach this in a manner as simple as possible?

score 43 · Accepted Answer · edited Nov 13 '11 at 16:36

43

Create a new empty array, add each of your arrays to that, then use call_user_func_array()

$wrkArray = array( $userArray1,
                   $userArray2,
                   $userArray3
                 );
$result = call_user_func_array('array_intersect',$wrkArray);

edited Nov 13 '11 at 16:36

Josh

10,961
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answered Mar 22 '11 at 10:01

Mark Baker

209,507
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385

Already tried that, as mentioned in the link in my original question. This is the error I get: "Warning: array_intersect() [function.array-intersect]: at least 2 parameters are required, 1 given in..." – Swader Mar 22 '11 at 10:18
Silly me, I missed the "_array" part of call_user_func! Thank you! – Swader Mar 22 '11 at 10:29
1

@swader - it's an easy mistake to make... don't kick yourself too much over it :-) – Mark Baker Mar 22 '11 at 10:44

score 4 · Answer 2 · answered Dec 03 '16 at 15:34

4

$arrays = [
    $userArray1,
    $userArray2,
    $userArray3
];
$result = array_intersect(...$arrays);

answered Dec 03 '16 at 15:34

lulco

524
2
11

rik · Answer 3 · 2011-03-22T17:56:19.887

3

Don't use eval()!

Try this

$isect = array();
for ($i = 1; $i <= $N; $i++) {
    $isect = array_intersect($isect, ${'array'.$i});
}

or that

$arrays = array()
for ($i = 1; $i <= $N; $i++) {
    $arrays[] = ${'array'.$i};
}
$isect = call_user_func_array('array_intersect', $arrays);

edited Mar 22 '11 at 17:56

answered Mar 22 '11 at 10:04

rik

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1

Please use **${'array' . $i}** if you really go this way. – eisberg Mar 22 '11 at 10:21
The first option doesn't work, because the result is initialized to an empty array, the result of the following intersects will always be an empty array. – Matt Nolan Jun 16 '17 at 13:09

score 1 · Answer 4 · answered Apr 12 '17 at 17:43

1

I am posting my answer very very late, but just want to share a small piece of code that helps me ,in case somebody needs it for this question.

print_r(array_intersect(array_merge($array1,$array2,...),$intersectionArr);

I hope this helps

Thanks

answered Apr 12 '17 at 17:43

jagpreet

84
1
6

score -1 · Answer 5 · edited May 06 '18 at 20:03

-1

Use the splat operator (...) as in: array_intersect(...$arrayOfArrays) or interchangeably call_user_func_array.

It's in the code in this tutorial: https://www.youtube.com/watch?v=AMlvtgT3t4E

edited May 06 '18 at 20:03

Floern

33,559
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answered May 02 '18 at 07:40

phpme

1

Intersect unknown number of arrays in PHP

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