Since PHP 5.5, you can use array_column
:
$ids = array_column($users, 'id');
This is the preferred option on any modern project. However, if you must support PHP<5.5, the following alternatives exist:
Since PHP 5.3, you can use array_map
with an anonymous function, like this:
$ids = array_map(function ($ar) {return $ar['id'];}, $users);
Before (Technically PHP 4.0.6+), you must create an anonymous function with create_function
instead:
$ids = array_map(create_function('$ar', 'return $ar["id"];'), $users);