replace duplicate fom stdclass array php

Question

When I print $online_performers variable I want to get a unique value for id 2. Do I need to convert them in standard array first or is that possible without it? (remove all duplicates).Please check my new code for this.

 Array
        (
            [0] => stdClass Object
            (
                [id] => 1
                [username] => Sample1
            )
            [1] => stdClass Object
            (
                [id] => 2
                [username] => Sample1
            )
           [2] => stdClass Object
            (
                [id] => 2
                [username] => Sample1
            )
           [3] => stdClass Object
            (
                [id] => 4
                [username] => Sample4
            )
        )



to
    Array
        (
            [0] => stdClass Object
            (
                [id] => 1
                [username] => Sample1
            )
            [1] => stdClass Object
            (
                [id] => 4
                [username] => Sample4
            )
        )

Answer 1

PHP has a function called array_filter() for that purpose:

$filtered = array_filter($array, function($item) {
    static $counts = array();
    if(isset($counts[$item->id])) {
        return false;
    }

    $counts[$item->id] = true;
    return true;
});

Note the usage of the static keyword. If used inside a function, it means that a variable will get initialized just once when the function is called for the first time. This gives the possibility to preserve the lookup table $counts across multiple function calls.

---

In comments you told, that you also search for a way to remove all items with id X if X appears more than once. You could use the following algorithm, which is using a lookup table $ids to detect elements which's id occur more than ones and removes them (all):

$array = array("put your stdClass objects here");

$ids = array();
$result = array();

foreach($array as $item) {
    if(!isset($ids[$item->id])) {
        $result[$item->id]= $item;
        $ids[$item->id] = true;
    } else {
        if(isset($result[$item->id])) {
            unset($result[$item->id]);
        }
    }
}

$result = array_values($result);
var_dump($result);

Answer 2

Let's say we have:

$array = [
   //items 1,2,3 are same
   (object)['id'=>1, 'username'=>'foo'],
   (object)['id'=>2, 'username'=>'bar'],
   (object)['id'=>2, 'username'=>'baz'],
   (object)['id'=>2, 'username'=>'bar']
];

Then duplication depends of what do you mean. For instance, if that's about: two items with same id are treated as duplicates, then:

$field = 'id';

$result = array_values(
   array_reduce($array, function($c, $x) use ($field)
   {
      $c[$x->$field] = $x;
      return $c;
   }, [])
);

However, if that's about all fields, which should match, then it's a different thing:

$array = [
   //1 and 3 are same, 2 and 3 are not:
   (object)['id'=>1, 'username'=>'foo'],
   (object)['id'=>2, 'username'=>'bar'],
   (object)['id'=>2, 'username'=>'baz'],
   (object)['id'=>2, 'username'=>'bar']
];

You'll need to identify somehow your value row. Easiest way is to do serialize()

$result = array_values(
   array_reduce($array, function($c, $x)
   {
      $c[serialize($x)] = $x;
      return $c;
   }, [])
);

But that may be slow since you'll serialize entire object structure (so you'll not see performance impact on small objects, but for complex structures and large amount of them it's sounds badly)

Also, if you don't care about keys in resulting array, you may omit array_values() call, since it serves only purpose of making keys numeric consecutive.

Answer 3

If you don't care about changing your keys you could do this with a simple loop:

$aUniq = array ();
foreach($array as $obj) {
    $aUniq[$obj->id] = $obj;
}

print_r($aUniq);