As for taking first key of an array, it's much more efficient to RESET and then KEY, rather then RESET result of ARRAY_KEYS (as sugested by gardnerjohng at gmail dot com).
<?php
reset($someArray);
echo key($someArray);
?>
This will give the same result but is much much faster. Larger arrays, better performance. Tested on 100-elements long array with 16 times faster results.