PhP Create array from huge string

I am retrieving a huge string from the WoW Armory API using:

$allAchievements = file_get_contents('http://us.battle.net/api/wow/data/character/achievements');

That returns this:

http://us.battle.net/api/wow/data/character/achievements

I am trying to convert this into a manageable format such as an array that would look similar to:

[achievements]=> array
             (
            [0]=> Array 
               (
                [id]=>6, 
                [title]=>Level 10, 
                [points]=>10, 
                [description]=>Reach Level 10.,
                [rewardItems]=>[],
                [icon]=>achievement_level_10,
                [criteria]=>[],
                [accountWide]=>false,
                [factionId]=>2,
                )
            [1]=> Array 
               (
                [id]=>7, 
                [title]=>Level 20, 
                [points]=>10, 
                [description]=>Reach Level 20.,
                [rewardItems]=>[],
                [icon]=>achievement_level_20,
                [criteria]=>[],
                [accountWide]=>false,
                [factionId]=>2,
                ) 
               ... 
              )

I have tried numerous combinations of explode() and parse_str() but i haven't been able to create any kind of array that would prove to be any use to me.

Is there a way to use file_get_contents(); so that a array would be returned in stead of a string?

If not, where should i start to expand this huge string into a manageable array?

Thank You for any help!