PHP - Array unique only using specific values

Question

I have a PHP array that looks like this...

Array
(
    [0] => Array
    (
        [id] => 1
        [value] => 111
        [date] => 'today'
    )

[1] => Array
    (
        [id] => 2
        [value] => 222
        [date] => 'today'
    )

[2] => Array
    (
        [id] => 3
        [value] => 333
        [date] => 'today'
    )

[3] => Array
    (
        [id] => 1
        [value] => 111
        [date] => 'today'
    )

[4] => Array
    (
        [id] => 5
        [value] => 111
        [date] => 'today'
    )

)

If I use array_unique like this...

print_r(array_unique($array, SORT_REGULAR));

It removes the duplicate [3] which is correct, but I am looking for a way to ignore [id] and only match by [date] and [value] so that my output looks like this...

Array
(
    [0] => Array
    (
        [id] => 1
        [value] => 111
        [date] => 'today'
    )

[1] => Array
    (
        [id] => 2
        [value] => 222
        [date] => 'today'
    )

[2] => Array
    (
        [id] => 3
        [value] => 333
        [date] => 'today'
    )

)

Iterate over array and store found pairs date-value. If pair exists - skip array item. — u_mulder
– u_mulder, Commented Feb 18, 2018 at 17:42

RomanPerekhrest · Accepted Answer · 2018-02-18 17:49:47Z

array_reduce + array_values() solution:

$arr = [
    ['id' => 1, 'value' => 111, 'date'=> 'today'],
    ['id' => 2, 'value' => 222, 'date'=> 'today'],
    ['id' => 3, 'value' => 333, 'date'=> 'today'],
    ['id' => 1, 'value' => 111, 'date'=> 'today'],
    ['id' => 5, 'value' => 111, 'date'=> 'today']
    ];

$result = array_values(
    array_reduce($arr, function($r, $a){
        if (!isset($r[$a['value'] . $a['date']])) $r[$a['value'] . $a['date']] = $a;
        return $r;
    }, [])
);

print_r($result);

The output:

Array
(
    [0] => Array
        (
            [id] => 1
            [value] => 111
            [date] => today
        )

    [1] => Array
        (
            [id] => 2
            [value] => 222
            [date] => today
        )

    [2] => Array
        (
            [id] => 3
            [value] => 333
            [date] => today
        )
)

u_mulder · Accepted Answer · 2018-02-18 17:45:14Z

1

Iterate over your array and get a key as concatenation of 'date' and 'value' fields. If this key has already been found - skip array value:

$pairs = [];
$new_values = [];
foreach ($array as $item) {
    $key = $item['date'] . $item['value'];

    if (empty($pairs[$key])) {
        $pairs[$key] = 1;
        $new_values[] = $item;
    }
}

answered Feb 18, 2018 at 17:45

u_mulder

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2 Comments

fightstarr20 Over a year ago

Does your solution differ in speed or resources from RomanPerekhrests version?

u_mulder Over a year ago

You can compare this yourself. But I don't think you will find significant difference. And unless your array has millions of records you won't even feel the difference.

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