bit manipulation - PHP - converting bitmask -

say assign following fruits:

array ('1' => 'apple', '2' => 'banana', '4' => 'grape', '8' => 'orange')

if wanted represent apple , banana, following: 0001 or 0010 0011 (or 3), right?

given number 3, how convert 1 , 2?

all keys loaded $keys:

$keys = array(); $value = 3;  foreach ($arr $key => $val) {    if ($value & $key)    {       $keys[] = $key;    } }