How to remove ALL duplicate values from an array in PHP? - php

Question

I want to check only the value [id] for duplicates, and remove all keys where this "field" [id] is a duplicate.
Example: If I have numbers 1,2,1. I want the result to be 2, not 1,2. And criteria for duplicates is determined only by checking [id], not any other "field".
Original array:
Array
(
[0] => Array
(
[name] => John
[id] => 123
[color] => red
)
[1] => Array
(
[name] => Paul
[id] => 958
[color] => red
)
[2] => Array
(
[name] => Jennifer
[id] => 123
[color] => yellow
)
)
The result I want:
Array
(
[0] => Array
(
[name] => Paul
[id] => 958
[color] => red
)
)

Answer 1

I agree with everyone above, you should give us more information about what you've tried, but I like to code golf, so here's a completely unreadble solution:
$new_array = array_filter($array, function($item) use (&$array){
return count(array_filter($array, function($node) use (&$item){
return $node['id'] == $item['id'];
})) < 2;
});

Answer 2

This should be fairly easy to accomplish with a couple of simple loops:
set_time_limit(0); // Disable time limit to allow enough time to process a large dataset
// $items contains your data
$id_counts = array();
foreach ($items as $item) {
if (array_key_exists($item['id'], $id_counts)) {
$id_counts[$item['id']]++;
} else {
$id_counts[$item['id']] = 1;
}
}
for ($i = count($items); $i >= 0; $i--) {
if ($id_counts[$items[$i]['id']] > 1) {
array_splice($items, $i, 1);
}
}
Result:
Array
(
[0] => Array
(
[name] => Paul
[id] => 958
[color] => red
)
)
While there are neater ways to do it, one advantage of this method is you're only creating new arrays for the list of ids and duplicate ids and the array_splice is removing the duplicates from the original array, so memory usage is kept to a minimum.
Edit: Fixed a bug that meant it sometimes left one behind

Answer 3

This is a very basic approach to the answer and I am sure there are much better answers however I would probably start by doing it the way I would on paper.
I look at the first index, check its value. Then I go through every other index making note of their index if the value is the same as my originally noted value. Once I have gone through the list if I have more than one index with that particular value I remove them all (starting with the highest index, so as to not affect indexes of the others while deleting).
Do this for all other indexes till you reach the end of the list.
It is long winded but will make sure it removes all values which have duplicates. and leaves only those which originally had no duplicates.

Answer 4

function PickUniques(array $items){
// Quick way out
if(empty($items)) return array();
$counters = array();
// Count occurences
foreach($items as $item){
$item['id'] = intval($item['id']);
if(!isset($counters[$item['id']])){
$counters[$item['id']] = 0;
}
$counters[$item['id']]++;
}
// Pop multiples occurence ones
foreach($counters as $id => $occurences){
if($occurences > 1){
unset($counters[$id]);
}
}
// Keep only those that occur once (in $counters)
$valids = array();
foreach($items as $item){
if(!isset($items[$item['id']])) continue;
$valids[$item['id']] = $item;
}
return $valids;
}
Try this one :)