If you need to change the name of a key without changing its position in the array this function may be useful.

<?php
function array_key_change($Old, $New, $In, $NewVal=NULL) {
        $Temp = array();
        while(isset($Temp[$Old]) == false) {
                list($k, $v) = each($In);
                $Temp[$k] = $v;
                unset($In[$k]);
        }
        if($NewVal == NULL) {
                $NewVal = $Temp[$Old];
        }
        unset($Temp[$Old]);
        $Temp = array_reverse($Temp);
        $In = array_merge(array($New=>$NewVal), $In);
        while(list($k,$v) = each($Temp)) {
                $In = array_merge(array($k=>$v), $In);
        }
        return($In);
}
?>