PHP Reorder array of objects based on contents of another array

I have an array of objects that is being generated from an SQL query within a custom Joomla! 1.5 component:

$query = 'SELECT * FROM #__orders_hearaboutus ORDER BY id';
$this->_hearaboutus = $this->_getList($query);

This generates something like:

Array
(
    [0] => stdClass Object
        (
            [id] => 3
            [how_heard] => Our Website
        )

    [1] => stdClass Object
        (
            [id] => 4
            [how_heard] => Other Website
        )

    [2] => stdClass Object
        (
            [id] => 5
            [how_heard] => Word of Mouth
        )

    [3] => stdClass Object
        (
            [id] => 6
            [how_heard] => Other
        )

    [4] => stdClass Object
        (
            [id] => 10
            [how_heard] => Internet Search Engine
        )

    [5] => stdClass Object
        (
            [id] => 11
            [how_heard] => Local Newspaper
        )

    [10] => stdClass Object
        (
            [id] => 16
            [how_heard开发者_StackOverflow中文版] => Leaflet by Post
        )

    [11] => stdClass Object
        (
            [id] => 18
            [how_heard] => Club or Society Newsletter
        )

)

This is then generating an HTML select 'Where did you hear about us' drop-down option within an order form.

What I'd like to do is to re-order the list by supplying the IDs in the desired (arbitrary) order, assuming that an array is the best way to do this:

$ordering = array(11,3,4,10,16,5,18,6);

I've found ways of reordering arrays in this way or reordering arrays of objects by keys but I can't work out how to achieve the above?

---

The most straight-forward way is to do it in SQL:

$query = 'SELECT * FROM ... ORDER BY FIELD(id,11,3,4,10,16,5,18,6)';

http://dev.mysql.com/doc/refman/5.0/en/string-functions.html#function_field

Since it's really not good practice to use arbitrary primary keys as sort criterium, you should really add an additional order column for that purpose.

---

You can do this in MySQL like @deceze mentioned or in PHP, using array_multisort():

array_multisort($this->_hearaboutus, $ordering, SORT_ASC);

---

Doing it via MySQL as mentioned by @deceze is probably the best way of doing it, but here's a quick and dirty way of achieving what you need.

class testObj {
    public $id;
    function __construct($id) {
        $this->id = $id;
    }
}

$order = array( 11, 3, 4, 10, 16, 5, 18, 6);
$objects = array(
    new testObj(3),
    new testObj(4),
    new testObj(5),
    new testObj(6),
    new testObj(10),
    new testObj(11),
    new testObj(16),
    new testObj(18)
);

$neworder = array();

foreach ( $order as $ord ) {

    foreach ( $objects as $obj ) {

        if ( $obj->id == $ord ) {
            $neworder[] = $ord;
        }

    }

}

print_r( $neworder );