iPhone non-stop disconnecting from USB (no other ports)

I have a Macbook Pro 2015 with retina and an iPhone 5s. Recently, very all of a sudden, whenever I try to plug my phone into the computer via the USB, it connects and disconnects nonstop so much that my phone is literally one continuous vibration until I turn it off. It's not the cable, because when I plug it into the wall with the block it behaves perfectly, and it isn't my USB ports because every other device works just fine when plugged into either of the ports. I have tried resetting SMC and PRAM.

This is making it very difficult to sync or charge my iPhone and I'd really appreciate some help. Both of my devices are only a year old.