How to displays keys of an array?

I have an array looking so:

Array
(
 [0] => a
 [1] => b
 [3] => c
 [4] => d
 [15] => e
)

and i want to get something like that:

开发者_如何学PythonArray
(
 [0] => a
 [1] => b
 [2] => c
 [3] => d
 [4] => e
)

How do I get the intended effect?

---

array_values($array)

Easy as pie :)

---

$new_array = array_values($old_array); //this will return sorted  one