Array
(
    [746] => 3
    [208] => 2
    [1091] => 1
    [313] => 1
    [305] => 1
    [707] => 1
)

Array (
    [0] => 746
    [1] => 208
    [2] => 1091
    [3] => 313
    [4] => 305
    [5] => 707 )

$newArray = array_keys($oldArray)