Selecting a few unique, random array items by shuffling keys

MGeary helped me clean a complex function—containing many lines and loops—up into four concise lines by utilizing the shuffle function. I thought that I would posted it here in case it helps anyone else. I was trying to randomly select five unique items from a multi-dimensional array and although I had achieved the results I wanted, his suggetion allowed me to shorten my code considerably.

$howmany_want = 5;
$author_keys = array_keys($authors);
shuffle($author_keys);
$author_keys = array_slice($author_keys, 0, $howmany_want);