PHP prevent duplicates when building an array

Question

I am building an array like this: (this happens in a loop)

$IDs[] = ID;

But I want to prevent that the same ID is being entered mulitple times, is there any way I can prevent this from happening?

Many thanks in advance!!

Use [`in_array()`](http://php.net/manual/en/function.in-array.php) function to test. — Rajdeep Paul, Apr 19 '16 at 15:12
Possible duplicate of [How to remove duplicate values from an array in PHP](http://stackoverflow.com/questions/307650/how-to-remove-duplicate-values-from-an-array-in-php) — Henders, Apr 19 '16 at 15:17

Andreas · Accepted Answer · 2016-04-19T15:14:54.337

3

Use array_unique. It will remove duplicates.

It will not prevent you from adding duplicates but when your looping is done you can just do:
$arr = array_unique($arr);

EDIT: Jay gave a good solution too in the comments.

edited Apr 19 '16 at 15:14

answered Apr 19 '16 at 15:09

Andreas

Thanks didn't know it existed! – Frank Lucas Apr 19 '16 at 15:15
@FrankLucas No problem. I updated with one more line in my answer – Andreas Apr 19 '16 at 15:15
Is there a way I can reset the keys? I now get [0] and [3] as keys it should be [0] and [1] :) – Frank Lucas Apr 19 '16 at 15:20
@FrankLucas Maybe this. http://ca2.php.net/manual/en/function.array-values.php not sure though – Andreas Apr 19 '16 at 15:23
@FrankLucas To reset keys use [`array_values()`](http://php.net/manual/en/function.array-values.php) function. – Rajdeep Paul Apr 19 '16 at 15:24

DocRattie · Answer 2 · 2018-08-27T12:14:40.827

2

$IDs[$ID] = $ID;

This is a simple way to ensure that every ID is only once in your array.

Even thought array_unique works as well, I think this is a faster and easier way.

edited Aug 27 '18 at 12:14

answered Apr 19 '16 at 15:29

DocRattie

1

also note that array_unique() will retain the FIRST item in the array, while this technique will ensure that the latest entry is in the array. In many cases you want the most recent entry, not the oldest. – Danial Jul 22 '18 at 18:15

2 Answers2