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    array_uintersect

    (PHP 5, PHP 7, PHP 8)

    array_uintersect — Computes the intersection of arrays, compares data by a callback function

    Description

    array_uintersect(array $array, array ...$arrays, callable $value_compare_func): array

    Computes the intersection of arrays, compares data by a callback function.

    Parameters

    array

    The first array.

    arrays

    Arrays to compare against.

    value_compare_func

    The comparison function must return an integer less than, equal to, or greater than zero if the first argument is considered to be respectively less than, equal to, or greater than the second.

    callback(mixed $a, mixed $b): int
    Caution

    Returning non-integer values from the comparison function, such as float, will result in an internal cast to int of the callback's return value. So values such as 0.99 and 0.1 will both be cast to an integer value of 0, which will compare such values as equal.

    Caution

    The sorting callback must handle any value from any array in any order, regardless of the order they were originally provided. This is because each individual array is first sorted before being compared against other arrays. For example:

    <?php
    $arrayA     = ["string", 1];
    $arrayB = [["value" => 1]];
    // $item1 and $item2 can be any of "string", 1 or ["value" => 1]
    $compareFunc = static function ($item1, $item2) {
    $value1 = is_string($item1) ? strlen($item1) : (is_array($item1) ? $item1["value"] : $item1);
    $value2 = is_string($item2) ? strlen($item2) : (is_array($item2) ? $item2["value"] : $item2);
    return     $value1 <=> $value2;
    };
    ?>

    Return Values

    Returns an array containing all the values of array that are present in all the arguments.

    Examples

    Example #1 array_uintersect() example

    <?php
    $array1     = array("a" => "green", "b" => "brown", "c" => "blue", "red");
    $array2 = array("a" => "GREEN", "B" => "brown", "yellow", "red");

    print_r(array_uintersect($array1, $array2, "strcasecmp"));
    ?>

    The above example will output:

    Array
(
    [a] => green
    [b] => brown
    [0] => red
)

    See Also

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    User Contributed Notes 4 notes

    up
    17
    Nate at RuggFamily dot com
    17 years ago
    I want to stress that in the user function, you do need to return either a 1 or a -1 properly; you cannot simply return 0 if the results are equal and 1 if they are not.

    The following code is incorrect:

    <?php
    function myfunction($v1,$v2)
    {
    if (    $v1===$v2)
    {
    return     0;
    }
    return     1;
    }

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

    This code is correct:

    <?php
    function myfunction($v1,$v2)
    {
    if (    $v1===$v2)
    {
    return     0;
    }
    if (    $v1 > $v2) return 1;
    return -    1;
    }
    $a1=array(1, 2, 4);
    $a2=array(1, 3, 4);
    print_r(array_uintersect($a1,$a2,"myfunction"));
    ?>
    up
    4
    Ryan C
    2 years ago
    If you're rolling your own comparison function, keep in mind that the spaceship operator (i.e. <=>) can be your best friend. It's been around since PHP7. https://www.php.net/manual/en/language.operators.comparison.php

    So, for instance, instead of a clunky function like:

    <?php
    function myFunction($v1, $v2) {
    if (    $v1 === $v2) {
    return     0;
    }
    if (    $v1 > $v2) return 1;
    return -    1;
    }
    ?>

    You can simplify it to:

    <?php
    function myFunction($v1, $v2) {
    return     $v1 <=> $v2;
    }
    ?>
    up
    3
    rob dot c dot ruiz at gmail dot com
    6 years ago
    When trying to do a case insensitive comparison between arrays of words, the strcasecmp function works very nicely with this one like so:

    $arr1 = array('blue', 'green', 'red');

    $arr2 = array('BLUE', 'Purple', 'Red');

    $loose_matches = array_uintersect($arr1, $arr2, 'strcasecmp');

    print_r($loose_matches) // array('blue', 'red');
    up
    3
    Hayley Watson
    6 years ago
    As for the other "compare function" callbacks, the return value from the callback function doesn't need to be -1, 0, or 1.

    cmp($a,$b) just needs to be <0, =0, or >0 depending on whether $a<$b, $a=$b, or $a>$b.
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