How to re-key array with non-sequential numeric keys

I have an array:

Array
(
 [0] => ololo
 [2] => test
 [3] => haha
 [7] => nice
)

How can I change the indexes of the array to this:

Array
(
 [0] => ololo
 [1] => test
 [2] => haha
 [3] => nice
)