Just a useful version which returns a simple array with the first key and value. Porbably a better way of doing it, but it works for me ;-)

<?php

function array_kshift(&$arr)
{
  list($k) = array_keys($arr);
  $r  = array($k=>$arr[$k]);
  unset($arr[$k]);
  return $r;
}

// test it on a simple associative array
$arr = array('x'=>'ball','y'=>'hat','z'=>'apple');

print_r($arr);
print_r(array_kshift($arr));
print_r($arr);

?>

Output:

Array
(
    [x] => ball
    [y] => hat
    [z] => apple
)
Array
(
    [x] => ball
)
Array
(
    [y] => hat
    [z] => apple
)