<?php

$countries = array(
  0 => '-- SELECT --',
  1 => 'Afghanistan',
  2 => 'Albania',
  3 => 'Algeria',
  4 => 'American Samoa',
  5 => 'Andorra',
  22 => 'Canada',
  44 => 'United States',);
  
$favourites = array(0, 44, 22);

$ordered = array();
foreach($favourites as $id)
{
    $ordered[$id] = $countries[$id];
}

$ordered += array_diff_assoc($countries, $ordered);

print_r($ordered);

Array
(
    [0] => -- SELECT --
    [44] => United States
    [22] => Canada
    [1] => Afghanistan
    [2] => Albania
    [3] => Algeria
    [4] => American Samoa
    [5] => Andorra
)