Having a brain freeze over a fairly trivial problem. If I start with an array like this:
$my_array = array(
\'monkey\' => array(...),
array_shift is probably less efficient than unsetting the index, but it works:
$my_array = array('monkey' => 1, 'giraffe' => 2, 'lion' => 3);
$my_array['monkey'] = array_shift($my_array);
print_r($my_array);
Another alternative is with a callback and uksort:
uksort($my_array, create_function('$x,$y','return ($y === "monkey") ? -1 : 1;'));
You will want to use a proper lambda if you are using PHP5.3+ or just define the function as a global function regularly.