Description:
------------
When i make a for in a array associative, but using some wrong key like numeric, this crash the system.
Please see the code 

Reproduce code:
---------------
protected function getArray() {
    $days = array();
    for ($i = 31; $i > 0; $i--) {
        $day  = mktime (0, 0, 0, date("m")  , date("d")-$i, date("Y"));
        if (date('w', $day) != 0 && date('w', $day) != 6 ){
            $days[] = date('d/m/Y', $day);
        }
    }
    $days = array_flip($days);
    for ($i = 0; $i < count($days); $i++) {
//Here is the problem, becouse insted of use a correct key, i use a number. In this point the system crash.
        $days[$i] = 0;
    }
    return $days;
}