Create array out of sub arrays with same Key?

Question

I have an array called $friends with names and ids, gotten from the Facebook graph API.

If I print it, it look something like this:

Array (
  [0] => Array (
     [name] => Tom
     [id] => 21)
  [1] => Array (
     [name] => Bob
     [id] => 22)
)

How do I retrieve all Keys (ids) and create a new array like this one?

Array ( [0] => 21 [1] => 22 )

Answer 1

$ids = array_map(function ($friend) { return $friend['id']; }, $friends);

Note, uses PHP 5.3+ anonymous function syntax.

Answer 2

You can use a simple foreach.

$ids = array();
foreach($friends as $friend)
   $ids[] = $friend['id'];

Answer 3

foreach ($friends as $key => $value) {

    $newFriends[$key] = $value['id'];
}

Answer 4

$arFinal = array();
foreach ($friends as $key => $val){
    $arFinal[$key] = $val['id'];
}