I want a new iphone but if i dont pass my credit check can i get a co signer?

Yes a co-sign would allow you to purchase that phone easily. even if you both have horrible credit. Practically... My advice is dont do it tho, if there is nothing wrong with your old phone why replace it. Times is hard now-adays. I mean if you have an extra 100-150 or even 200 bucks a month to just blow to KEEP UP WITH THE JONES'S!! Be my guest,