How can i recover data from a dead iphone

Hi everyone. My old 4s iphone was dead a long time ago ( almost two years ). But when i bought a new ip which was 5s later that year, i received not all, but some of my pictures from the old phone, the lastest ones i suppose. I want to know why this happened and from that, can i recover my old pictures. Note that my 4s has been completely dead. I have not tried to connect it with my computer but i dont think it will work. So, again, the question is: why did i receive some of my photos from a dead iphone, and can i recover more due to this phenomenon. Thanks!!