Remove duplicates from an array based on object property?

Question

I have an array of objects. I'd like to remove the duplicates based on the "name" value in the object.

  [0]=>
  object(stdClass)#337 (9) {
    ["term_id"]=>
    string(2) "23"
    ["name"]=>
    string(12) "Assasination"
    ["slug"]=>
    string(12) "assasination"
  }
  [1]=>
  object(stdClass)#44 (9) {
    ["term_id"]=>
    string(2) "14"
    ["name"]=>
    string(16) "Campaign Finance"
    ["slug"]=>
    string(16) "campaign-finance"
  }
  [2]=>
  object(stdClass)#298 (9) {
    ["term_id"]=>
    string(2) "15"
    ["name"]=>
    string(16) "Campaign Finance"
    ["slug"]=>
    string(49) "campaign-finance-good-government-political-reform"
  }

So in this case, how do I remove the duplicate "Campaign Finance" object from the array. So the entire [2] object?

I've gone through a bunch of the PHP duplicate array question here, but none seemed to deal with objects and filtering just off of one parameter.

Answer 1

For php >=7.0:

Since array_column works on object-arrays since PHP 7.0 you can use the following combination as suggested by @plashenkov:

$filtered = array_intersect_key($array, array_unique(array_column($array, 'someProperty')));

Full example: https://3v4l.org/IboLu#v8.0.8

class my_obj
{
        public $term_id;
        public $name;
        public $slug;

        public function __construct($i, $n, $s)
        {
                $this->term_id = $i;
                $this->name = $n;
                $this->slug = $s;
        }
}

$objA = new my_obj(23, 'Assasination', 'assasination');
$objB = new my_obj(14, 'Campaign Finance', 'campaign-finance');
$objC = new my_obj(15, 'Campaign Finance', 'campaign-finance-good-government-political-reform');

$array = array($objA, $objB, $objC);
echo 'Original array:\n';
print_r($array);

/** Answer Code begins here */
$filtered = array_intersect_key($array, array_unique(array_column($array, 'name')));
/** Answer Code ends here */

echo 'After removing duplicates\n';
print_r($filtered);

Output:

Original array:
Array
(
    [0] => my_obj Object
        (
            [term_id] => 23
            [name] => Assasination
            [slug] => assasination
        )

    [1] => my_obj Object
        (
            [term_id] => 14
            [name] => Campaign Finance
            [slug] => campaign-finance
        )

    [2] => my_obj Object
        (
            [term_id] => 15
            [name] => Campaign Finance
            [slug] => campaign-finance-good-government-political-reform
        )

)
After removing duplicates
Array
(
    [0] => my_obj Object
        (
            [term_id] => 23
            [name] => Assasination
            [slug] => assasination
        )

    [1] => my_obj Object
        (
            [term_id] => 14
            [name] => Campaign Finance
            [slug] => campaign-finance
        )

)

The object with term_id 15 was removed as it had the same name as term_id 14.

For php <7.0:

Build a new array with the existing keys and just the name as value, use array_unique (note that it preserves keys).

Then copy every key from the original array to a new array ($filtered) (or remove everything thats not in the unique'ed array from the original key-wise).

Edit: Complete example: https://3v4l.org/SCrko#v5.6.40

class my_obj
{
        public $term_id;
        public $name;
        public $slug;

        public function __construct($i, $n, $s)
        {
                $this->term_id = $i;
                $this->name = $n;
                $this->slug = $s;
        }
}

$objA = new my_obj(23, 'Assasination', 'assasination');
$objB = new my_obj(14, 'Campaign Finance', 'campaign-finance');
$objC = new my_obj(15, 'Campaign Finance', 'campaign-finance-good-government-political-reform');

$array = array($objA, $objB, $objC);

echo 'Original array:\n';
print_r($array);

/** Answer Code begins here **/

// Build temporary array for array_unique
$tmp = array();
foreach($array as $k => $v)
    $tmp[$k] = $v->name;

// Find duplicates in temporary array
$tmp = array_unique($tmp);

// Build new array with only non-duplicate items
$filtered = [];
foreach($array as $k => $v)
{
    if (array_key_exists($k, $tmp))
        $filtered[$k] = $v;
}

/** Answer Code ends here **/

echo 'After removing duplicates\n';
print_r($filtered);

Output:

Original array:
Array
(
    [0] => my_obj Object
        (
            [term_id] => 23
            [name] => Assasination
            [slug] => assasination
        )

    [1] => my_obj Object
        (
            [term_id] => 14
            [name] => Campaign Finance
            [slug] => campaign-finance
        )

    [2] => my_obj Object
        (
            [term_id] => 15
            [name] => Campaign Finance
            [slug] => campaign-finance-good-government-political-reform
        )

)
After removing duplicates
Array
(
    [0] => my_obj Object
        (
            [term_id] => 23
            [name] => Assasination
            [slug] => assasination
        )

    [1] => my_obj Object
        (
            [term_id] => 14
            [name] => Campaign Finance
            [slug] => campaign-finance
        )

)

The object with term_id 15 was removed as it had the same name as term_id 14.

Answer 2

One-liner:

$filtered = array_intersect_key($array, array_unique(array_column($array, 'someProperty')));

Please note that array_column() works with array of objects in PHP 7 and newer.