Remove duplicates from a multi-dimensional array based on 2 values

Question

I have an array that looks like this

$array = array(
  array("John","Smith","1"),
  array("Bob","Barker","2"),
  array("Will","Smith","2"),
  array("Will","Smith","4")
);

In the end I want the array to look like this

$array = array(
  array("John","Smith","1"),
  array("Bob","Barker","2"),
  array("Will","Smith","2")
);

The array_unique with the SORT_REGULAR flag checks for all three value. I've seen some solutions on how to remove duplicates based on one value, but I need to compare the first two values for uniqueness.

So collect values in array and check if something is already there. — u_mulder
– u_mulder, Commented Mar 9, 2017 at 20:16
Loop and build array with the key as a concatenation of both. — AbraCadaver
– AbraCadaver, Commented Mar 9, 2017 at 20:18
Two answers keep array("Will","Smith","2") and one can keep either array("Will","Smith","2") or array("Will","Smith","4") since you didn't specify if it was important. — AbraCadaver
– AbraCadaver, Commented Mar 9, 2017 at 20:39

RomanPerekhrest · Accepted Answer · 2017-03-09 20:49:14Z

3

Simple solution using foreach loop and array_values function:

$arr = array(
          array("John","Smith","1"), array("Bob","Barker","2"), 
          array("Will","Smith","2"), array("Will","Smith","4")
);

$result = [];
foreach ($arr as $v) {
    $k = $v[0] . $v[1];  // considering first 2 values as a unique key
    if (!isset($result[$k])) $result[$k] = $v;
}

$result = array_values($result);
print_r($result);

The output:

Array
(
    [0] => Array
        (
            [0] => John
            [1] => Smith
            [2] => 1
        )

    [1] => Array
        (
            [0] => Bob
            [1] => Barker
            [2] => 2
        )

    [2] => Array
        (
            [0] => Will
            [1] => Smith
            [2] => 2
        )
)

edited Mar 9, 2017 at 20:49

answered Mar 9, 2017 at 20:18

RomanPerekhrest

93.1k4 gold badges75 silver badges112 bronze badges

Sign up to request clarification or add additional context in comments.

5 Comments

AbraCadaver Over a year ago

No need to check if key exists. Keys will be unique. If it's important that the first one be retained then loop in reverse.

RomanPerekhrest Over a year ago

@AbraCadaver, I don't think so. If I omit a key check the last value will be array("Will","Smith","4") but the OP posted an exact output with exact values where the last is array("Will","Smith","2")

AbraCadaver Over a year ago

Yes, that's why I said if it's important to keep the first then just array_reverse before and after.

RomanPerekhrest Over a year ago

@AbraCadaver, I can not say that array_reverse approach is quite bad. But foreach - array_values approach is over 4 times faster(tested on 1000 iterations, PHP 5.6)

John Baker Over a year ago

@RomanPerekhrest Such a simple solutions. Can't say I would've come up with your version on my own, but now I wonder why I didn't think of merging two values and placing them into a new array and then use in_array on each loop to check for a duplicate. Thank you.

u_mulder · Accepted Answer · 2017-03-09 20:18:28Z

0

Sample code with comments:

// array to store already existing values
$existsing = array();
// new array
$filtered = array();

foreach ($array as $item) {
    // Unique key
    $key = $item[0] . ' ' . $item[1];

    // if key doesn't exists - add it and add item to $filtered
    if (!isset($existsing[$key])) {
        $existsing[$key] = 1;
        $filtered[] = $item;
    }
}

answered Mar 9, 2017 at 20:18

u_mulder

54.8k5 gold badges54 silver badges72 bronze badges

1 Comment

AbraCadaver Over a year ago

No need to check if key exists. Keys will be unique. If it's important that the first one be retained then loop in reverse.

AbraCadaver · Accepted Answer · 2017-03-09 20:35:45Z

0

For fun. This will keep the last occurrence and eliminate the others:

$array = array_combine(array_map(function($v) { return $v[0].$v[1]; }, $array), $array);

Map the array and build a key from the first to entries of the sub array
Use the returned array as keys in the new array and original as the values

If you want to keep the first occurrence then just reverse the array before and after:

$array = array_reverse($array);
$array = array_reverse(array_combine(array_map(function($v) { return $v[0].$v[1]; },
                                               $array), $array));

edited Mar 9, 2017 at 20:35

answered Mar 9, 2017 at 20:28

AbraCadaver

79.2k7 gold badges75 silver badges91 bronze badges

4 Comments

RomanPerekhrest Over a year ago

can the OP obtain array("Will","Smith","2") as the last value with this solution?

AbraCadaver Over a year ago

@RomanPerekhrest Yes, the second example does that since they didn't specify.

Jonathan Over a year ago

seems like this code will perform poorly given larger data sets.

Jonathan Over a year ago

You can benchmark it. It's ugly too. The other answers are better.

Collectives™ on Stack Overflow

Remove duplicates from a multi-dimensional array based on 2 values

3 Answers 3

5 Comments

1 Comment

4 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

5 Comments

1 Comment

4 Comments

Your Answer

Sign up or log in

Post as a guest

Related