Filter out rows of a 2d array if the row is not found in another 2d array

Question

I've written this code:

$aArray = [
    [0, 0, 0], 
    [1, 0, 0], 
    [2, 0, 0], 
    [3, 0, 0], 
    [4, 0, 0], 
    [5, 0, 0], 
    [6, 0, 0], 
    [7, 0, 0], 
];

$jump = [
    [0, 0, 0], 
    [1, 0, 0], 
    [9, 7, 4], 
    [3, 0, 0], 
    [4, 0, 0], 
    [5, 0, 0], 
    [6, 0, 0], 
    [7, 0, 0], 
];
var_dump(array_intersect($aArray, $jump));

the result I'm getting is this:

array(8) { 
[0]=> array(3) { 
    [0]=> int(0) 
    [1]=> int(0) 
    [2]=> int(0) } 
[1]=> array(3) { 
    [0]=> int(1) 
    [1]=> int(0) 
    [2]=> int(0) } 
[2]=> array(3) { 
    [0]=> int(2) 
    [1]=> int(0) 
    [2]=> int(0) } 
[3]=> array(3) { 
    [0]=> int(3) 
    [1]=> int(0) 
    [2]=> int(0) } 
[4]=> array(3) { 
    [0]=> int(4) 
    [1]=> int(0) 
    [2]=> int(0) } 
[5]=> array(3) { 
    [0]=> int(5) 
    [1]=> int(0) 
    [2]=> int(0) } 
[6]=> array(3) { 
    [0]=> int(6) 
    [1]=> int(0) 
    [2]=> int(0) } 
[7]=> array(3) { 
    [0]=> int(7) 
    [1]=> int(0) 
    [2]=> int(0) } 
    }

Why isn't the second index getting filtered out? I've tried emptying my cache in case it had old values stored in there. I've also noticed that if I delete the last array from the jump array, it still produces 7,0,0. Is this a weird anomaly?

AbraCadaver · Accepted Answer · 2015-05-09 18:33:52Z

2

array_intersect() is not recursive, it sees the inner arrays as just an array. You would need to use something like this:

function array_intersect_recursive() {

    foreach(func_get_args() as $arg) {
        $args[] = array_map('serialize', $arg);
    }
    $result = call_user_func_array('array_intersect', $args);

    return array_map('unserialize', $result);
}

$result = array_intersect_recursive($aArray, $jump);

answered May 9, 2015 at 18:33

AbraCadaver

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1 Comment

upndown Over a year ago

thanks @AbraCadaver. I suspected it had something to do with requiring a recursive function. very helpful. I also figured out that when it's returning the intersect point, if a nested array has at least one key/ value match, it will return the entire thing because it's returning the first parameter's keys.

mickmackusa · Accepted Answer · 2024-12-17 00:11:30Z

0

To filter the first array by the second array by comparing the full-row data, use array_uintersect() to be able to access the second level of the arrays.

Code: (Demo)

var_export(array_uintersect($aArray, $jump, fn($a, $b) => $a <=> $b));

If you want to make row-for-row comparisons pairing rows by their first-level key, then use array_uintersect_assoc().

Code: (Demo)

var_export(array_uintersect_assoc($aArray, $jump, fn($a, $b) => $a <=> $b));

Because of the all rows except [2] have the same first level key and row payload, both snippets above return the exact same result.

If you move the last row of $jump to be its first row, then array_unintersect_assoc() will return no rows, but array_uintersect() will still return all but [2]. Demo

edited Dec 17, 2024 at 0:11

answered Jun 24, 2024 at 1:00

mickmackusa♦

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