<?php

function promoteMembers($input, $membersToPromote)
{
    $diff = array_diff($input, $membersToPromote);
    return array_merge($membersToPromote, $diff);
}

$first = array("a", "b", "c", "d", "e");
$second = array("b", "c");

var_dump( promoteMembers($first, $second) );

?>

array(5) {
  [0]=>
  string(1) "b"
  [1]=>
  string(1) "c"
  [2]=>
  string(1) "a"
  [3]=>
  string(1) "d"
  [4]=>
  string(1) "e"
}