Array Unique with Associative Array - Remove Duplicates

Question

I've got an associative array with some duplicate items. For example, I have:

 <? 
 $group_array = array('user_id'=>array(), 'user_first'=>array());

Which outputs something like below:

Array
 (
[user_id] => Array
    (
        [0] => 594
        [1] => 597
        [2] => 594
    )

[user_first] => Array
    (
        [0] => John
        [1] => James
        [2] => John
    )
)

I'd like to sanitize this entire array so that only the user John will show up once (based on user_id).

I've tried the following:

 <?php 
   $unique = array_unique($group_array);
   print_r($unique);

But it does not appear to work. Any other ideas how I can remove the duplicate items in the array?

Any help would be great!

salathe · Accepted Answer · 2011-02-02 13:02:54Z

3

Another approach would be to find the unique user_ids, and importantly their array keys, then keep only the corresponding values from each of the columns.

$group_array = array(
    'user_id'    => array(594,    597,     594,    598   ),
    'user_first' => array('John', 'James', 'John', 'John'),
);

// Find unique user_ids
$uniques = array_unique($group_array['user_id']);

// Keep only the uniques
foreach ($group_array as $column => $collection) {
    $group_array[$column] = array_intersect_key($collection, $uniques);
}

print_r($group_array);

answered Feb 2, 2011 at 13:02

salathe

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Comments

Deep Kapadia · Accepted Answer · 2011-02-02 09:03:53Z

1

Couple of things:

the array_unique function does not recurse into sub arrays

Read the manual: http://php.net/manual/en/function.array-unique.php "Two elements are considered equal if and only if (string) $elem1 === (string) $elem2. In words: when the string representation is the same. The first element will be used."

In your case $elem1 and $elem2 are both arrays

answered Feb 2, 2011 at 9:03

Deep Kapadia

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Comments

automatix · Accepted Answer · 2016-05-20 22:30:16Z

A possible solution is to use the filtering side effect of array_combine(...):

$array = [
    'user_id' => [
        0 => 594,
        1 => 597,
        2 => 594
    ],
    'user_first' => [
        0 => 'John',
        1 => 'James',
        2 => 'John'
    ]
];

$combinedArray = array_combine($array['user_id'], $array['user_first']);

So we got the array

Array
(
    [594] => John
    [597] => James
)

To restore the original structure we simply can extract the keys and the values:

$array = [
    'user_id' => array_keys($combinedArray),
    'user_first' => array_values($combinedArray),
];

Result:

Array
(
    [user_id] => Array
        (
            [0] => 594
            [1] => 597
        )

    [user_first] => Array
        (
            [0] => John
            [1] => James
        )
)

Toto · Accepted Answer · 2011-02-02 12:34:03Z

This script removes duplicates on user_id and keeps multiple firstnames if their ids are different:

$group_array = Array(
    'user_id' => Array(
        594,
        597,
        594,
        598,
    ),
    'user_first' => Array(
        'John',
        'James',
        'John',
        'John',
    )
);

$dup = array();
for ($i=0; $i<count($group_array['user_id']); $i++) {
    if (in_array($group_array['user_id'][$i], $dup)) {
        unset($group_array['user_id'][$i]);
        unset($group_array['user_first'][$i]);
    } else {
        $dup[] = $group_array['user_id'][$i];
    }
}
print_r($group_array);

output:

Array
(
    [user_id] => Array
        (
            [0] => 594
            [1] => 597
            [3] => 598
        )

    [user_first] => Array
        (
            [0] => John
            [1] => James
            [3] => John
        )

)

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