How to query posts that have certain post meta keys, and sort by meta key and/or value

by

how about array_reverse()

http://php.net/manual/en/function.array-reverse.php

there are a bunch of array manipulation functions at php.net. i’m always there looking something up. also sort() might be useful

EDIT based on your comments:

sort($album);
print_r($album);

should return:

Array
(
    [0] => 001,Get Rich Or Die Tryin
    [1] => 002,Curtis
    [2] => 003,The Massacre
    [3] => 004,Before I Self Destruct
)