Iphones can't sync to itunes, but can sync to PC

Hi,

I have a iphone 4 for about a year now, and it can sync to itunes just fine, til now...

So now I have purchased a new iphone 5 and wish to transfer my whatsapp text history on the old iphone 4 to the new phone, and using itunes backup appears to be the only way of doing so (upon my research).

However, neither of these two iphones can sync to itunes.

Though the iphones can't sync to itunes, it seems to have no problem syncing to the PC, as the chargeing screen appears when I have my iphones connected to the PC.

I had followed the steps on Apple support, it can't solve the problem.

I had tried to reinstall itunes several times, it still can't fix the problem.

I had also tried an alternative tools, ifunbox, but it can't sync to ifunbox neither.

I assume it is a hardware problem??

I am no expert on gadgets, Can anyone help me pls😟???