Shuffle an array in PHP
As $bb is an array of arrays, shuffle() won't randomise the sub-array, try shuffle on the nested array as follows:
shuffle($bb['slides']);
You probably shuffled the outer $bb array, when you should have done:
shuffle($bb['slides']);
foreach($bb['slides'] as $b):
shuffle($array_name); // will shuffle array
http://www.php.net/manual/en/function.shuffle.php
Also the foreach should be
for($array_name as $array_item) {
// do stuff
}