which one should be used to manipulating data, Array or Array Object? Like search,sort and other array manipulations.
The basic type is array. This is a map of keys and values that can be written to, read from and accessed in a loop.
The ArrayObject is a class that you can extend to create objects that behave as if they were arrays. It implements methods like count and sort that enable you to treat an object like you would treat an array. It's part of the SPL (Standard PHP Library).
Typically you'd use array. You'll know when you need ArrayObject.